Re: RFR: 8347408: Create an internal method handle adapter for system calls with errno [v15]

[Per Minborg]

> Going forward, converting older JDK code to use the relatively new FFM API 
> requires system calls that can provide `errno` and the likes to explicitly 
> allocate a MemorySegment to capture potential error states. This can lead to 
> negative performance implications if not designed carefully and also 
> introduces unnecessary code complexity.
> 
> Hence, this PR proposes to add a _JDK internal_ method handle adapter that 
> can be used to handle system calls with `errno`, `GetLastError`, and 
> `WSAGetLastError`.
> 
> It currently relies on a thread-local cache of MemorySegments to allide 
> allocations. If, in the future, a more efficient thread-associated allocation 
> scheme becomes available, we could easily migrate to that one.
> 
> Here are some benchmarks:
> 
> 
> Benchmark                                        Mode  Cnt   Score   Error  
> Units
> CaptureStateUtilBench.explicitAllocationFail     avgt   30  41.615 ? 1.203  
> ns/op
> CaptureStateUtilBench.explicitAllocationSuccess  avgt   30  23.094 ? 0.580  
> ns/op
> CaptureStateUtilBench.threadLocalFail            avgt   30  14.760 ? 0.078  
> ns/op
> CaptureStateUtilBench.threadLocalReuseSuccess    avgt   30   7.189 ? 0.151  
> ns/op
> 
> 
> Explicit allocation:
> 
>         try (var arena = Arena.ofConfined()) {
>             return (int) HANDLE.invoke(arena.allocate(4), 0, 0);
>         }
> 
> 
> Thread Local (tl):
> 
>         return (int) ADAPTED_HANDLE.invoke(arena.allocate(4), 0, 0);
> 
> 
> The graph below shows the difference in latency for a successful call:
> 
> ![image](https://github.com/user-attachments/assets/58fbef01-5d06-406c-87e6-75f468227fc6)
> 
> This is a ~3x improvement for both the happy and the error path.
> 
> 
> Tested and passed tiers 1-3.

Per Minborg has updated the pull request incrementally with one additional 
commit since the last revision:

  Break out the pool to a separate package and reorganize code

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/22391/files
  - new: https://git.openjdk.org/jdk/pull/22391/files/410508ed..8ff211b1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22391&range=14
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22391&range=13-14

  Stats: 408 lines in 4 files changed: 336 ins; 28 del; 44 mod
  Patch: https://git.openjdk.org/jdk/pull/22391.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22391/head:pull/22391

PR: https://git.openjdk.org/jdk/pull/22391