RFR: 8364819: Post-integration cleanups for JDK-8359820 [v9]

[Anton Artemov]

> Hi, please consider the following changes:
> 
> This is a cleanup after https://github.com/openjdk/jdk/pull/26309
> 
> 1) `_handshake_timed_out_thread `and `_safepoint_timed_out_thread` are now `Thread*` and not `intptr_t`, no conversions `p2i <-> i2p` needed.
> 
> 2) Added a missed brace in the error message. 
> 
> 3) Updates are done with `Atomic::replace_if_null()` to address possible multiple updates and visibility among all threads. 
> 
> Trivial change.

Anton Artemov has updated the pull request incrementally with one additional commit since the last revision:

  8364819:  Addressed reviewer's comments

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/26656/files
  - new: https://git.openjdk.org/jdk/pull/26656/files/b833bf5d..ee4ceadb

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26656&range=08
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26656&range=07-08

  Stats: 6 lines in 1 file changed: 2 ins; 2 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/26656.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26656/head:pull/26656

PR: https://git.openjdk.org/jdk/pull/26656