Compound expressions conversions

* Ensure that we track additional member symbols in the VB binder context and populate the additional field/property symbols initialized by VB AsNew clause that initializes more than one field/property

Note: This change also includes an API change to `IPropertyInitializer` as VB WithEvents declaration with AsNew clause initializer can initialize multiple properties.
Fixes #17813

* Fix wording in some comments

* Address review feedback

* Fix build break

Add IgnoredArguments to IVariableDeclarator.

Update static instance handling

Rewrite IPlaceholderOperation to IConditionalAccessInstanceOperation …

Trivial renames of IOperation API parameter names

* dotnet/master: (28 commits)
  Fix the operation verifier code now that getoperationinternal no longer exists.
  Remove usage of IOperation feature flag in newly added unit tests
  More fixes for IOperation tree. (#23028)
  Address PR feedback and remove unused resource and comment out unused error code
  Remove IOperation feature flag and internal registration APIs for operations
  Add unit test for VB
  Address review feedback and add more unit tests
  Fix unit tests
  Fix build errors from merge resolution
  Revert unintentional newline deletion
  Address recent feedback and do not generate an IParenthesizedOperation for C#. This change is now just a test-only change that verifies the current behavior.
  Address PR feedback and use singleton for null instance
  Address PR feedback
  Address PR feedback
  Do not invoke GetStandaloneNode helper in GetOperationWorker
  Fix InvalidCastException in CSharpOperationFactory for invalid nested member initializer (#22983)
  Use ICollection<string>.Contains to avoid Enumerator allocation
  Add IsRef property to IConditionalOperation and ISimpleAssignmentOperation, add RefKind property to ILocalSymbol. (#22933)
  Enable peverify-compat mode for langver < 7.2 (#22772)
  Fix IArgument and IArrayInitializer to have null types
  ...

This was missed as part of #22774 for #22719.
Fixes #22719

Extract conversion and binary operator logic into reusable components, and refactor all instances to use it.

Fix the operation verifier code now that getoperationinternal no long…

* fix_verifier:
  Fix the operation verifier code now that getoperationinternal no longer exists.

* dotnet/master: (36 commits)
  Remove usage of IOperation feature flag in newly added unit tests
  More fixes for IOperation tree. (#23028)
  Address PR feedback and remove unused resource and comment out unused error code
  Remove IOperation feature flag and internal registration APIs for operations
  Add unit test for VB
  Address review feedback and add more unit tests
  Fix unit tests
  Fix build errors from merge resolution
  Revert unintentional newline deletion
  Address recent feedback and do not generate an IParenthesizedOperation for C#. This change is now just a test-only change that verifies the current behavior.
  Address PR feedback and use singleton for null instance
  Address PR feedback
  Address PR feedback
  Do not invoke GetStandaloneNode helper in GetOperationWorker
  Fix InvalidCastException in CSharpOperationFactory for invalid nested member initializer (#22983)
  Use ICollection<string>.Contains to avoid Enumerator allocation
  Add IsRef property to IConditionalOperation and ISimpleAssignmentOperation, add RefKind property to ILocalSymbol. (#22933)
  Enable peverify-compat mode for langver < 7.2 (#22772)
  Properly detect root of a tree in Operation.SearchParentOperation (#22974)
  Fix IArgument and IArrayInitializer to have null types
  ...

Port change to remove IOperation feature flag from dev15.5.x to master

Do not invoke GetStandaloneNode helper in GetOperationWorker

Fixes #23004.
Fixes #23009.
Related to #22548 and #22229.