Add documentation for /reportanalyzer command line switch (#11348)

https://github.com/dotnet/roslyn/issues/6149

docs/analyzers/Report Analyzer Format.md

+Introduction
+============
+The C# and Visual Basic compilers support a /reportanalyzer switch on
+the command line to report additional analyzer information, such as execution time.
+
+The output contains the total wall clock time spent in executing the analyzers and
+the relative execution times per-analyzer.
+Note that the elapsed time may be less than analyzer execution time because
+analyzers can run concurrently. One should use this data only for comparitive analysis to
+identify any outlier analyzer which takes signinficantly more time than other analyzers.
+
+
+Output Format
+=============
+
+```
+Total analyzer execution time: XYZ seconds.
+NOTE: Elapsed time may be less than analyzer execution time because analyzers can run concurrently.
+```
+Time (s)  | % |  Analyzer
+----------|---|----------------------
+xyz1      | X |  Analyzer Assembly Identity
+xyz2      | Y |    -    DiagnosticAnalyzer1
+xyz3      | Z |    -    DiagnosticAnalyzer2
+
+
+Example
+=============
+
+Following is an example output from a project built with analyzers:
+
+-------------------------------------------------------------------------------------------------------
+```
+Total analyzer execution time: 0.503 seconds.
+NOTE: Elapsed time may be less than analyzer execution time because analyzers can run concurrently.
+
+Time (s)    %   Analyzer
+   0.242   48   Roslyn.Diagnostics.CSharp.Analyzers, Version=1.2.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
+   0.240   47      Roslyn.Diagnostics.Analyzers.CSharpCodeActionCreateAnalyzer
+   0.002   <1      Roslyn.Diagnostics.Analyzers.CSharp.CSharpSpecializedEnumerableCreationAnalyzer
+  <0.001   <1      Roslyn.Diagnostics.Analyzers.CSharp.CSharpDiagnosticDescriptorAccessAnalyzer
+  <0.001   <1      Roslyn.Diagnostics.Analyzers.CSharpSymbolDeclaredEventAnalyzer
+
+   0.137   27   System.Runtime.Analyzers, Version=1.2.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
+   0.045    8      System.Runtime.Analyzers.AttributeStringLiteralsShouldParseCorrectlyAnalyzer
+   0.024    4      System.Runtime.Analyzers.SpecifyStringComparisonAnalyzer
+   0.022    4      System.Runtime.Analyzers.SpecifyIFormatProviderAnalyzer
+   0.020    3      System.Runtime.Analyzers.ProvideCorrectArgumentsToFormattingMethodsAnalyzer
+   0.009    1      System.Runtime.Analyzers.CallGCSuppressFinalizeCorrectlyAnalyzer
+   0.007    1      System.Runtime.Analyzers.DisposableTypesShouldDeclareFinalizerAnalyzer
+   0.003   <1      System.Runtime.Analyzers.NormalizeStringsToUppercaseAnalyzer
+   0.003   <1      System.Runtime.Analyzers.InstantiateArgumentExceptionsCorrectlyAnalyzer
+   0.002   <1      System.Runtime.Analyzers.TestForNaNCorrectlyAnalyzer
+   0.001   <1      System.Runtime.Analyzers.DoNotUseEnumerableMethodsOnIndexableCollectionsInsteadUseTheCollectionDirectlyAnalyzer
+  <0.001   <1      System.Runtime.Analyzers.SpecifyCultureInfoAnalyzer
+  <0.001   <1      System.Runtime.Analyzers.DoNotLockOnObjectsWithWeakIdentityAnalyzer
+  <0.001   <1      System.Runtime.Analyzers.TestForEmptyStringsUsingStringLengthAnalyzer
+  <0.001   <1      System.Runtime.Analyzers.AvoidUnsealedAttributesAnalyzer
+
+   0.085   16   Roslyn.Diagnostics.Analyzers, Version=1.2.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
+   0.085   16      Roslyn.Diagnostics.Analyzers.DeclarePublicAPIAnalyzer
+
+   0.023    4   System.Runtime.CSharp.Analyzers, Version=1.2.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
+   0.014    2      System.Runtime.Analyzers.CSharpAvoidZeroLengthArrayAllocationsAnalyzer
+   0.008    1      System.Runtime.Analyzers.CSharpInitializeStaticFieldsInlineAnalyzer
+   0.001   <1      System.Runtime.Analyzers.CSharpDoNotRaiseReservedExceptionTypesAnalyzer
+  <0.001   <1      System.Runtime.Analyzers.CSharpUseOrdinalStringComparisonAnalyzer
+  <0.001   <1      System.Runtime.Analyzers.CSharpDoNotUseTimersThatPreventPowerStateChangesAnalyzer
+  <0.001   <1      System.Runtime.Analyzers.CSharpDisposeMethodsShouldCallBaseClassDisposeAnalyzer
+
+   0.006    1   System.Runtime.InteropServices.CSharp.Analyzers, Version=1.2.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
+   0.006    1      System.Runtime.InteropServices.Analyzers.CSharpAlwaysConsumeTheValueReturnedByMethodsMarkedWithPreserveSigAttributeAnalyzer
+  <0.001   <1      System.Runtime.InteropServices.Analyzers.CSharpMarkBooleanPInvokeArgumentsWithMarshalAsAnalyzer
+  <0.001   <1      System.Runtime.InteropServices.Analyzers.CSharpUseManagedEquivalentsOfWin32ApiAnalyzer
+
+   0.004   <1   System.Runtime.InteropServices.Analyzers, Version=1.2.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
+   0.004   <1      System.Runtime.InteropServices.Analyzers.PInvokeDiagnosticAnalyzer
+
+   0.004   <1   System.Collections.Immutable.Analyzers, Version=1.2.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
+   0.004   <1      System.Collections.Immutable.Analyzers.DoNotCallToImmutableArrayOnAnImmutableArrayValueAnalyzer
+
+   0.001   <1   System.Threading.Tasks.Analyzers, Version=1.2.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
+   0.001   <1      System.Threading.Tasks.Analyzers.DoNotCreateTasksWithoutPassingATaskSchedulerAnalyzer
+
+   0.001   <1   XmlDocumentationComments.CSharp.Analyzers, Version=1.2.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
+   0.001   <1      XmlDocumentationComments.Analyzers.CSharpAvoidUsingCrefTagsWithAPrefixAnalyzer
+```
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