[lworld] RFR: 8368031: Apply mainline changes to support preview mode work into Valhalla

[David Beaumont]

This change rolls up four necessary (and hopefully sufficient) mainline changes needed in Valhalla for the preview mode work.

These were applied bottom-to-top in a Valhalla repo by applying patches created from a recent mainline JDK repo, using "git show" and "git apply".

Note that I needed to use "--theirs" to resolve a small set of mismatches due to other non-exact patching which has already occurred for these classes. I see no intermediate changes in any classes by anyone else, no sign of overwriting other changes, and internal testing is passing. I would have preferred if everything applied 100% clean, but things like copyright years were fixed in one version and not in the other.

[Apply patch from mainline hash: 3fae6013c6]
8365532: java/lang/module/ModuleReader/ModuleReaderTest.testImage fails

[Apply patch from mainline hash: 0b05b7cc92]
8365436: ImageReaderTest fails when jmods directory not present

[Apply patch from mainline hash: 06ce9e89ab]
8365467: Issues with jrtfs implementation for exploded run-time images

[Apply patch from mainline hash: 166210719e]
8367005: ImageReader refactor caused performance regressions for startup and footprint

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Commit messages:
 - Apply patch from mainline hash: 166210719e
 - Apply patch from mainline hash: 06ce9e89ab
 - Apply patch from mainline hash: 0b05b7cc92
 - Apply patch from mainline hash: 3fae6013c6

Changes: https://git.openjdk.org/valhalla/pull/1600/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1600&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8368031
  Stats: 568 lines in 9 files changed: 456 ins; 44 del; 68 mod
  Patch: https://git.openjdk.org/valhalla/pull/1600.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1600/head:pull/1600

PR: https://git.openjdk.org/valhalla/pull/1600