VB EnC: when lowering conditional branches produce a pattern that allows the debugger to perform function remapping

Remove unnecessary data and implementation details from XML produced by PdbToXml. Update PDB tests accordingly.
The removed data include sizes and versions of CDI blobs, counts of elements (redundant since the elements themselves are included in the XML), hidden sequence point line/columns, etc.

This change only affects tests. (changeset 1395517)

New format "TStaticType" indicates the presence of "using StaticType;" in source.

Interaction is between the compiler and the expression compiler, so no VS integration test is required.

CR: VSadov; AlekseyT (changeset 1376703)

Removes UnoptimizedDll/unoptimizedExe and other /optimize & /debug option combinations from tests.
Fixes bug in C# EE - we have incorrectly treated end offset of a local scope as inclusive. It's exclusive for C#, inclusive for VB. (changeset 1313100)

Stores Encoding on SourceText so that we can always calculate checksum of the underlying binary data, even if the SourceText wasn’t created from a Stream.

Adds WithRootAndOptions and WithFilePath methods to SyntaxTree and implements them for all subclasses. I decided to merge WithRoot and WithOptions to a single method WithRootAndOptions since setting one without the other doesn't make much sense (the options should correspond to the root node).

Propagates the Encoding throughout workspaces and services.
Refactors recoverable syntax trees so that they can implement With* methods.

Allow encoding on SourceText to be unspecified (null) and report an emit diagnostic when attempting to emit debug information for a syntax tree that is backed by encoding-less source text. If user creates a syntax tree from a string they previously read from a file and then try to emit debuggable compilation with such tree the original encoding of the file might not match the default UTF8 (they might different by presence of BOM, which is quite subtle). To avoid confusion we don't set UTF8 encoding by default. Instead we report the diagnostic and the user needs to explicitly provide an encoding to the syntax tree factory method.

Avoid leaking DecoderFallbackException out of EncodedStringText.Create. Throw InvalidDataException instead to reduce the amount of exceptions that the caller needs to deal with.

Also moves HasSameText extension method from Services to SourceText and optimizes the comparison for the case we the SHA1 checksums are available.
 (changeset 1260412)