Fixes #12214

* Separating warning messages for constant filter expression
* Deal with try-catch with finally block and add test

This reverts commit 75687b52.

* In parameters cannot have Out attributes

* PR feedback

* Follow up

* Clean up

* Test fixes

* Fix failing test

- "in" argument matches only "in" parameters (as opposed to unmodified case that can also match byval parameters)
- "in" requires that the argument is an lvalue
- "in" does not allow conversions at the call-site other than identity conversions
- "in" sets an exact bound in generic method type inference
- "in" cannot be stack-spilled by value

* fixed breaking changes markdown file

* Ban illegal assignment expressions

* Replacing conversions with a bound converted node

* Clean up

* PR comments

* Code comments

Addressed PR comments.

minor tweaks to cascaded error reporting

Removed ReturnableReference value kind. The returnability will be computed and validated separately from value kinds now.

* Add tests for basic `private protected` functionality.
* Constrain private protected to language version 7.2.
* Add tests for VB, and adjust existing VB tests as needed.
* Add test for SyntaxFacts production of source for private protected.
* Add VB tests corresponding to all C# tests for private protected
* Mention `private protected` in the compiler test plan.

* Stack alloc parsed to spans

* PR feedback

* Document the breaking change

* Compare lines instead of using AssertXml when validating PDBs.

AssertXml doesn't validate ordering.

* Reorder expected PDB XML nodes to match actual order

* Update to the latest Microsoft.DiaSymReader.* packages.

* Enable embedding sources to Windows PDBs