Fix clashing variable names generated by InstanceOfPatternMatch

[arodionov]

In addition to the cursor scope, added the enclosing J.If scope for searching conflicting variable names.

• Fix InstanceOfPatternMatch declares variable with conflicting name #334
• Fix InstanceOfPatternMatch can produce name clashes #481
• Fix https://github.com/openrewrite/rewrite/issues/2787
• It also can be a workaround for VariableNameUtils#generateVariableName() should consider following statements rewrite#2776

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[github-actions]

Some suggestions could not be made:

• src/main/resources/META-INF/rewrite/examples.yml
  • lines 634-633
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[github-actions]

Some suggestions could not be made:

• src/main/resources/META-INF/rewrite/examples.yml
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  • lines 634-633
  • lines 679-695
  • lines 1228-1247
  • lines 1280-1279
  • lines 2309-2308
  • lines 2324-2336
  • lines 2773-2772
  • lines 2792-2803

[timtebeek]

Great to see these cleared out; I think there might still be an issue with a triple nested if, but since this is already an improvement for a common case I propose we merge as is, and can address any other cases if reported.