Bugfix: Preconditions of overloaded @BeforeTemplate methods are filtered away

[jevanlingen]

What's changed?

After

• Improve preconditions check #120

we should be able to create fitting preconditions with multiple @BeforeTemplates (so no breaking UsesType when not all @BeforeTemplate use that type, as mentioned in #119). But the code did not work for overloaded methods, because the key/value in a temporary precondition-map was replaced by the next overloaded method.

What's your motivation?

• Upgrade OpenRewrite Templating 1.19.1 -> 1.20.0 PicnicSupermarket/error-prone-support#1470 (review)

Checklist

• I've added unit tests to cover both positive and negative cases
• I've read and applied the recipe conventions and best practices
• I've used the IntelliJ IDEA auto-formatter on affected files