Audit all fixers in repo for missing FixAll support and add unit tests

[mavasani]

I found 2 cases where we have a code fix, but no FixAll support: #1380 and #1381. Additionally there are no FixAll unit tests in our repo. @ivanbasov is planning to add some FixAll test infrastructure support, and we should use that to ensure that we have FixAll tests for every single code fix that we ship.

[mavasani]

Tagging @jinujoseph @kuhlenh

[sharwell]

StyleCop Analyzers runs a Fix All test automatically for every code fix test.

[mavasani]

StyleCop Analyzers runs a Fix All test automatically for every code fix test.

We should do that too..

[mavasani]

Found one more: #1395

At this point, I am going to write an analyzer to warn when a CodeFixer does not override GetFixAllProvider.

[sharwell]

@mavasani Consider an exception if the analyzer has NoCodeFixAttribute applied to it.

[mavasani]

@sharwell I was planning to write an operation analyzer that fires if the fixer invokes RegisterCodeFix (or related) method, but does not override GetFixAllProvider.

[sharwell]

@mavasani 👍 That would even handle cases like this: https://github.com/DotNetAnalyzers/StyleCopAnalyzers/blob/90b322ac8b0ed6f4067c7a99e80cc834134ad54e/StyleCop.Analyzers/StyleCop.Analyzers.CodeFixes/DocumentationRules/SA1649CodeFixProvider.cs#L27-L32

[mavasani]

Audit is done, we have an analyzer to detect missing FixAll support and #1420 tracks adding unit tests.