1. Do not report error if non-final variable is reassigned
2. Report error in Java 15 if 'final' modifier is used
3. Allow specifying 'final' modifier on introduce variable
4. Support non-final variables in PatternVariableCanBeUsed inspection
5. Copy modifiers in PatternVariableCanBeUsed quick-fix
GitOrigin-RevId: d7b82261a018c9a48bcdcf237ade0d8c08f5978d