Fix deleting unused bindings with Haddock docs V2

[xsebek]

• Add test case from Fix deleting unused bindings with Haddock docs #4881 by @agam263
• Use the AST to get the associated comment range - its on the annotation of the signature L EpAnn SigD, not on the definition ValD
  • TODO: deal with GHC imcompatibility
  • TODO: filter the signature to match the identifier
    • TODO: use structured GHC message instead of Regex
• Closes Delete unused binding code action doesn't delete haddock #4876
• Closes Fix deleting unused bindings with Haddock docs #4881