RFR: Merge lworld [v2]

[David Simms]

> Merge lworld @jdk-18+2

David Simms has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 20 commits:

 - Merge branch 'lworld' into lqagain_merge_lworld_18_2
   
   Merge lworld @jdk-18+2
 - 8268908: Update test/jdk/valhalla/valuetypes tests to prepare for jtreg 6 and other clean up
 - 8268656: [lqagain] A few code chunks dealing with dual class scheme still left in
 - 8268358: [lworld] toString for primitive class should return `ClassName at hash`
   
   Reviewed-by: rriggs
 - 8268584: [lqagain] Javac tests should not needlessly hardcode toString() output
 - 8267597: [lworld] Withdraw all support for bifurcated class generation for primitive classes
   8268527: [lqagain] langtool tests need tweaks to run properly in an universe where -XDunifiedValRefClass is the default
 - 8268418: [lworld] VM assert illegal mirror klass when calling Class::getInterfaces on a flat array
   
   Reviewed-by: fparain
 - 8268399: [BACKOUT] [lworld] Tests must be update after core reflection changes for the L/Q model
 - 8268389: [lworld] Tests must be update after core reflection changes for the L/Q model
   
   Reviewed-by: hseigel
 - 8267948: [lword] Core reflection and method handles support for L/Q model
   
   Reviewed-by: fparain, rriggs
 - ... and 10 more: https://git.openjdk.java.net/valhalla/compare/85af6b56...f1fabd8b

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Changes: https://git.openjdk.java.net/valhalla/pull/450/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=450&range=01
  Stats: 4434 lines in 187 files changed: 1581 ins; 2015 del; 838 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/450.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/450/head:pull/450

PR: https://git.openjdk.java.net/valhalla/pull/450