[foreign-abi] RFR: Merge foreign-memaccess [v2]

[J.Duke]

> Hi all,
> 
> this is an _automatically_ generated pull request to notify you that there is 1 commit from the branch
> `foreign-memaccess`that can **not** be merged into the branch `foreign-abi`:
> The following files contains merge conflicts:
> 
> - src/jdk.incubator.foreign/share/classes/jdk/internal/foreign/AbstractMemorySegmentImpl.java
> - src/jdk.incubator.foreign/share/classes/jdk/internal/foreign/MemoryAddressImpl.java
> - src/jdk.incubator.foreign/share/classes/jdk/internal/foreign/NativeMemorySegmentImpl.java
> - test/jdk/java/foreign/TestNative.java
> 
> All Committers in this [project](https://openjdk.java.net/census#panama) have access to my [personal
> fork](https://github.com/openjdk-bot/panama-foreign) and can therefore help resolve these merge conflicts (you may want
> to coordinate who should do this). The following paragraphs will give an example on how to solve these merge conflicts
> and push the resulting merge commit to this pull request. The below commands should be run in a local clone of your
> [personal fork](https://wiki.openjdk.java.net/display/skara#Skara-Personalforks) of the
> [openjdk/panama-foreign](https://github.com/openjdk/panama-foreign) repository.  # Ensure target branch is up to date $
> git checkout foreign-abi $ git pull https://github.com/openjdk/panama-foreign.git foreign-abi
> 
> # Fetch and checkout the branch for this pull request
> $ git fetch https://github.com/openjdk-bot/panama-foreign.git +59:openjdk-bot-59
> $ git checkout openjdk-bot-59
> 
> # Merge the target branch
> $ git merge foreign-abi
> 
> When you have resolved the conflicts resulting from the `git merge` command above, run the following commands to create
> a merge commit:
> $ git add paths/to/files/with/conflicts
> $ git commit -m 'Merge foreign-memaccess'
> 
> 
> When you have created the merge commit, run the following command to push the merge commit to this pull request:
> 
> $ git push https://github.com/openjdk-bot/panama-foreign.git openjdk-bot-59:59
> 
> _Note_: if you are using SSH to push commits to GitHub, then change the URL in the above `git push` command accordingly.
> 
> Thanks,
> J. Duke

J. Duke has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes
the unrelated changes brought in by the merge/rebase. The pull request contains 252 additional commits since the last
revision:

 - Remove spurious changes
 - Merge branch 'foreign-abi' into openjdk-bot-59
 - 8253796: Consider making CValueLayout public.
   
   Reviewed-by: mcimadamore
 - 8253255: Investigate replacing ABI layout attributes with custom subtypes of ValueLayout
   
   Reviewed-by: mcimadamore
 - Transition back to java on safepoint poll slow-path when returning from an optimized native call
   
   Reviewed-by: mcimadamore
 - Automatic merge of foreign-memaccess into foreign-abi
 - Turn on downcall intrinsics by default
   
   Reviewed-by: mcimadamore
 - Automatic merge of foreign-memaccess into foreign-abi
 - 8253373: Add package-level javadoc for foreign linker support
   
   Reviewed-by: sundar, jvernee
 - 8253430: Improve the LibraryLookup API
   
   Reviewed-by: jvernee, sundar
 - ... and 242 more: https://git.openjdk.java.net/panama-foreign/compare/b6d387e1...b5de2312

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

Changes:
  - all: https://git.openjdk.java.net/panama-foreign/pull/364/files
  - new: https://git.openjdk.java.net/panama-foreign/pull/364/files/b6d387e1..b5de2312

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=364&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=364&range=00-01

  Stats: 67441 lines in 214 files changed: 67238 ins; 95 del; 108 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/364.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/364/head:pull/364

PR: https://git.openjdk.java.net/panama-foreign/pull/364