Add doAfterVisit(UnnecessaryParentheses) to generated recipes

[timtebeek]

What's your motivation?

Until we update the JavaTemplate to detect and insert parentheses around for instance binary expressions, we need a quick way to move along openrewrite/rewrite-migrate-java#271 ; With this change we're able to add parentheses to the templates defined there, which are then cleaned up through UnnecessaryParentheses.

Have you considered any alternatives or workarounds?

We could always add parentheses in the JavaTemplate Strings produced by TemplateProcessor here; that might be a bit excessive, but would prevent us from having to add those parentheses to rewrite-migrate-java.

Any additional context

• Add Apache Commons StringUtils refaster template replacements rewrite-migrate-java#271

[knutwannheden]

Another alternative would be for us to determine whether expressions are required or not at "insertion time"; i.e. we could add some kind of maybeParenthesize(Expression, Cursor) utility method. I imagine this could be useful in other recipes as well. But generating a doAfterVisit() is simpler of course.

My only worry with doAfterVisit() is that if a lot of modifications are made, then for each such modification we schedule one of these visitors. I wonder if we should either add an overload or another method (like doOnceAfterVisit()) or add a marker interface to visitors. For maybeAddImport() and maybeRemoveImport() we hand-coded this logic.

[knutwannheden]

Left one small comment. After that I am happy.