Re-enable test that verifies ref return cannot be inlined

Merge dev15.1.x into master

Make the csharp_compiler and hello_world tests run

And only run one copy of each

* Add tests to improve coverage of pattern-matching implementation and fix a crash.
Fixes #9542
Fixes #16876 (crash that is fixed)
Fixes #17088
Added tests for #17089 

Run scripts with their own working directories

Merge post-dev15 into master

Narrow location in diagnostics for lambda symbol to either the delegate keyword or the arrow (#16990)

When running csx scripts to collect perf tests, run each script with the working directory set to the directory of the script. This makes it *much* simpler to use relative paths for #r statements.

Update syntax generator to correctly write enums

Catch exceptions when gathering tests

Previously we would read/write enums as objects.  Now we correctly write them out as integers

Add CodeFix for CS0168 CS0129

Merge post-dev15 into master

Merge master into dev15.1.x

Fix parameter syntax

Fixes #14146

Allow specification of a test search directory

Dynamic member access and indexers are not safe to return by reference.

Ensure package is loaded by loading CPS project

Support `foreach` statements that use different type from enumerable

Check the type of conversion being used in the foreach statement before deciding if we should offer to convert it to var.

support creating remote session that doesn't require solution 

Fix dynamic analysis instrumentation for VB

* use io exception message

* disable Culture test

* run tests on english ui culture

* use hresult detection code that works cross-language

* fix indentation

* Only run FileShareDeleteCompatibility_Xplat on an english machine

* Brace on new line

move down diagnostic analyzer executor down to workspace layer since …

We insert a bound node of method call to `CreatePayload(Guid,int,int,ref bool[],int)` during instrumentation for each method,
however, the node of the 4th argument (of type bool[]), which is an array access (something like payloads[2],
where payload is of type bool[][]), is created as an RValue. As an result, in the IL generated for instrumentation,
the argument is the reference to an local variable instead of to the indexed element in the array. This will cause `CreatePayload`
to throw an exception when it tries to add a payload array for a method that already has a payload array created.

Tree perf all work

Run our Nuget package index in the OOP process.