RFR: 8358680: AOT cache creation fails: no strings should have been added [v4]

[Ioi Lam]

> Background: when writing the string table in the AOT cache, we do this:
> 
> 1. Find out the number of strings in the interned string table
> 2. Allocate Java object arrays that are large enough to store these strings. These arrays are used by `StringTable::lookup_shared()` in the production run.
> 3. Enter safepoint
> 4. Copy the strings into the arrays
> 
> This bug happened because:
> 
> - Step 1 is not thread safe, so it may be reading a stale version of `_items_count`
> - JIT compiler threads may create more interned strings after step 1
> 
> This PR attempts to fix both issues.

Ioi Lam has updated the pull request incrementally with one additional commit since the last revision:

  @coleep comments

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/25816/files
  - new: https://git.openjdk.org/jdk/pull/25816/files/57ceaa9c..ad8456e1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25816&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25816&range=02-03

  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/25816.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25816/head:pull/25816

PR: https://git.openjdk.org/jdk/pull/25816