[lworld] RFR: 8368988: [lworld] Rename classes in valhalla/inlinetypes to be distinct

[Marc Chevalier]

Various cleanup in test package `compiler.valhalla.inlinetypes`:
- rename duplicated classes so that IDEs are nice, resolve correctly. New names are a bit... arbitrary. I'm happy to rename name if anyone has opinions. When writing new tests, let's prefer nested classes if we can.
- add `package compiler.valhalla.inlinetypes;` where it was missing. IDEs like that, and I vaguely remember we should.
- fix flags to take the new path into account, new package, or class renaming. Please, try to pay attention to that: I've did multiple passes to catch'em all, but this is easy to miss.
- remove some useless `import`.
- some few typos in comments.
- maybe more?

Thanks,
Marc

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Commit messages:
 - Merge remote-tracking branch 'origin/lworld' into JDK-8368988
 - post rebase fixes
 - Fixes
 - Some cleanup

Changes: https://git.openjdk.org/valhalla/pull/1683/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1683&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8368988
  Stats: 1550 lines in 53 files changed: 42 ins; 54 del; 1454 mod
  Patch: https://git.openjdk.org/valhalla/pull/1683.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1683/head:pull/1683

PR: https://git.openjdk.org/valhalla/pull/1683