[Ignore Expressions][NFC] Refactor to better use `IgnoreExpr.h` and nits

Authored by eduucaldas on Mon, Aug 31, 9:03 AM.


[Ignore Expressions][NFC] Refactor to better use IgnoreExpr.h and nits

This change groups

  • Rename: ignoreParenBaseCasts -> IgnoreParenBaseCasts for uniformity
  • Rename: IgnoreConversionOperator -> IgnoreConversionOperatorSingleStep for uniformity
  • Inline IgnoreNoopCastsSingleStep into a lambda inside IgnoreNoopCasts
  • Refactor IgnoreUnlessSpelledInSource to make adequate use of IgnoreExprNodes

Differential Revision: https://reviews.llvm.org/D86880