Removed unnecessary diagnostic id checks

[vweijsters]

• Removed the .Where and if (...) conditions that check to see if a diagnostic ID is fixable. See discussion in Implement a code fix provider for SA1626 (SingleLineCommentsMustNotUseDocumentationStyleSlashes) #1441
• Fixed failing SA1513 unit test
• Modified CodeFixVerifier to only present supported diagnostics to a code fix provider

This is part 1 of the breakup of #1452

[codecov-io]

Current coverage is 79.75%

Merging #1625 into master will increase coverage by +0.21% as of 24bd74c

@@            master   #1625   diff @@
======================================
  Files          531     531       
  Stmts        31617   31536    -81
  Branches      8865    8838    -27
  Methods                          
======================================
+ Hit          25150   25153     +3
+ Partial       5165    5137    -28
+ Missed        1302    1246    -56

Review entire Coverage Diff as of 24bd74c

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[Maxwe11]

[sharwell]

Why are we not seeing an AppVeyor build failure due to the SA1513 test?

[sharwell]

Ah, looks like that test only runs the code fix, but doesn't have the assertions for diagnostics reported before/after the fix.

[sharwell]

👍