The AbstractSpeculationAnalyzer would check whether casting symbols
used in Invocable expressions would break semantics. However it was not
considering all MemberAccess to be potentially invokable. This Changes
the IsInvokable check to consider all MemberAccess expressions.

This fixes #28412.

* Rename Foo to Goo

* Rename ifoo to igoo

* Add back BOMs

These tests were all using WpfFact, but not actually doing anything
that required either WPF or an STA thread. We plan to enable
parallelization of Facts (but not WpfFacts), and this ensures we can
parallelize as many tests as possible.

Responding to peer review feedback. Updated to never consider user
defined narrowing conversions unnecessary.

Fixes #3161 and Fixes #3163

User Scenario:
User has code with narrowing conversion with an explicit cast.  We will
offer to remove the cast even though this will cause the code to not
compile.

Fix Description:
We previously never consulted optionstrict to determine if a
user-defined narrowing cast was necessary.  The fix in CastAnalyzer.vb
will check if the conversion is narrowing, if option strict is on, or if
we generate a warning on implicit narrowing conversions.  We also offer
to add a cast if an implicit conversion warning is given.

Testing:  Added regression tests + existing tests

Fix ITypeSymbolExtensions.IsOrDerivedFromExceptionType to handle type parameters constrained on Exception type or its subtype

Fixes https://github.com/dotnet/roslyn/issues/3254

User scenario: User writes code where they have explicit casts to a type parameter deriving from Exception type or its subtype. We will offer incorrect cast removal fixes to remove these explicit casts. Removing such casts will cause their code to not compile. Even worse, if they apply a FixAll occurrences code fix, then all such casts across their (document/project/solution) will be removed, causing tons of compile errors.

Fix description: IsOrDerivedFromExceptionType was only checking for base types of the given type symbol to detect if the type is an Exception type. We also need to handle type parameters which are constrained by Exception or its subtypes.

Testing: Added regression tests + existing tests.

For code snippets such as below: "Base M(Base b) => (Derived)b;", we currently offer cast removal for cast to derived. However, this involves an explicit/narrowing conversion and hence can lead to an exception or data loss. The only way to detect such redundant casts is via flow analysis, which is not currently in our scope.

Fix is to bail out early for such cast expressions. I have also fixed incorrect tests that were added to ensure the current behavior.

Fixes #2761

There are legitimate cases where removing a cast inside a string
interpolation can case the open brace of the interpolation to touch the
open brace on an array literal, resulting in a broken parse (i.e. `{{`).

This changes the Remove Unnecesary Cast code fix to add parentheses
outside of the cast rather than around the inner expression. Then, the
parenthesis simplifier has been updated to correctly handle the case
where an array literal touches the start of an interpolation:

Dim x = $"{({})}"

Fixes Issue #739.