RFR: 8366178: Implement JEP 526: Lazy Constants (Second Preview) [v21]

[Per Minborg]

> Implement JEP 526: Lazy Constants (Second Preview)
> 
> The lazy list/map implementations are broken out from `ImmutableCollections` to a separate class.
> 
> The old benchmarks are not moved/renamed to allow comparison with previous releases.
> 
> `java.util.Optional` is updated so that its field is annotated with `@Stable`.  This is to allow `Optional` instances to be held in lazy constants and still provide constant folding.

Per Minborg has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 107 commits:

 - Merge master
 - Rework toString implementations
 - Update after doc comments
 - Merge branch 'master' into lazy-constants
 - Revert the AbstractMap.keySet @Stable annotation
 - Update docs after comments
 - Improve method docs
 - Improve equals/hashCode document
 - Update wording on List/Map Object methods
 - Update javadocs
 - ... and 97 more: https://git.openjdk.org/jdk/compare/681dab72...f775aaf1

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Changes: https://git.openjdk.org/jdk/pull/27605/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27605&range=20
  Stats: 8482 lines in 60 files changed: 3875 ins; 4490 del; 117 mod
  Patch: https://git.openjdk.org/jdk/pull/27605.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27605/head:pull/27605

PR: https://git.openjdk.org/jdk/pull/27605