Fix generated Proguard rules not using valid fully qualified name

[mhelder]

This PR fixes https://github.com/ZacSweers/MoshiX/issues/624.

KotlinPoet's ClassName.toString() does not yield a valid fully qualified path for e.g. nested classes, or when backticks are used in the package name to escape reserved keywords. Instead, ClassName.reflectionName() should be used for that.

☝️ This is the only functional change.

The other changes in this PR are:

• Fix the existing tests asserting incorrect expected values. These tests started failing as soon as reflectionName() was used. 👌
• Add a test for https://github.com/ZacSweers/MoshiX/issues/624. I just cherry picked 3 reserved keywords per category. These could be extended to include more, or reduced to a single keyword. It's currently not optimised at all, as it simply repeats the compile -> validation cycle 3*3 times. (Compiling once would probably be more efficient, but also harder to do assertions on the output)

Thanks to @sav007 for the hint in https://github.com/ZacSweers/MoshiX/issues/415#issuecomment-1513553223

[ZacSweers]

You need to run spotless locally - ./gradlew spotlessApply --no-configuration-cache

[mhelder]

Done!

[ZacSweers]

Unfortunately looks like there's failing tests

[mhelder]

Ah sorry, my bad, I overlooked one existing test. Have pushed a fix, and this time ran the full test suite to make sure everything passes.

[ZacSweers]

Can you push one more (empty) commit to re-trigger CI? Looks like github had an outage when you pushed

[ZacSweers]

Thanks!