RFR: 8312522: Implementation of Foreign Function & Memory API [v2]

[Jorn Vernee]

> This patch contains the implementation of the foreign linker & memory API JEP for Java 22. The initial patch is composed of commits brought over directly from the [panama-foreign repo](https://github.com/openjdk/panama-foreign). The main changes found in this patch come from the following PRs:
> 
> 1. https://github.com/openjdk/panama-foreign/pull/836 Where previous iterations supported converting Java strings to and from native strings in the UTF-8 encoding, we've extended the supported encoding to all the encodings found in the `java.nio.charset.StandardCharsets` class.
> 2. https://github.com/openjdk/panama-foreign/pull/838 We dropped the `MemoryLayout::sequenceLayout` factory method which inferred the size of the sequence to be `Long.MAX_VALUE`, as this led to confusion among clients. A client is now required to explicitly specify the sequence size.
> 3. https://github.com/openjdk/panama-foreign/pull/839 A new API was added: `Linker::canonicalLayouts`, which exposes a map containing the platform-specific mappings of common C type names to memory layouts.
> 4. https://github.com/openjdk/panama-foreign/pull/840 Memory access varhandles, as well as byte offset and slice handles derived from memory layouts, now feature an additional 'base offset' coordinate that is added to the offset computed by the handle. This allows composing these handles with other offset computation strategies that may not be based on the same memory layout. This addresses use-cases where clients are working with 'dynamic' layouts, whose size might not be known statically, such as variable length arrays, or variable size matrices.
> 5. https://github.com/openjdk/panama-foreign/pull/841 Remove this now redundant API. Clients can simply use the difference between the base address of two memory segments.
> 6. https://github.com/openjdk/panama-foreign/pull/845 Disambiguate uses of `SegmentAllocator::allocateArray`, by renaming methods that both allocate + initialize memory segments to `allocateFrom`. (see the original PR for the problematic case)
> 7. https://github.com/openjdk/panama-foreign/pull/846 Improve the documentation for variadic functions.
> 8. https://github.com/openjdk/panama-foreign/pull/849 Several test fixes to make sure the `jdk_foreign` tests can pass on 32-bit machines, taking linux-x86 as a test bed.
> 9. https://github.com/openjdk/panama-foreign/pull/850 Make the linker API required. The `Linker::nativeLinker` method is not longer allowed to throw an `UnsupportedOperationException` on ...

Jorn Vernee has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 17 commits:

 - 8313894: Rename isTrivial linker option to critical
   
   Reviewed-by: pminborg, mcimadamore
 - 8313680: Disallow combining caputreCallState with isTrivial
   
   Reviewed-by: mcimadamore
 - Merge branch 'master' into JEP22
 - use immutable map for fallback linker canonical layouts
 - 8313265: Move the FFM API out of preview
   
   Reviewed-by: mcimadamore
 - 8313005: Ensure native access check can fold away
   
   Reviewed-by: mcimadamore
 - 8312981: Make the linker API required
   
   Reviewed-by: mcimadamore
 - 8312615: Ensure jdk_foreign tests pass on linux-x86
   
   Reviewed-by: mcimadamore
 - 8312186: TestStringEncodingFails for UTF-32
   
   Reviewed-by: mcimadamore
 - 8312059: Clarify the documention for variadic functions
   8310646: Javadoc around prototype-less functions might be incorrect
   
   Reviewed-by: mcimadamore
 - ... and 7 more: https://git.openjdk.org/jdk/compare/23fe2ece...74bbe721

-------------

Changes: https://git.openjdk.org/jdk/pull/15103/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15103&range=01
  Stats: 2817 lines in 230 files changed: 1239 ins; 894 del; 684 mod
  Patch: https://git.openjdk.org/jdk/pull/15103.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15103/head:pull/15103

PR: https://git.openjdk.org/jdk/pull/15103