RFR: 8329748: Change default value of AssertWXAtThreadSync to true

[Tobias Holenstein]

The debug flag `-XX:+AssertWXAtThreadSync` conservatively  checks for correct W^X thread state at possible safepoints or handshake. The flag is useful to detect missing `MACOS_AARCH64_ONLY(ThreadWXEnable __wx(WXWrite, thread));`. Since the check is cheap and it is a `AARCH64_ONLY(develop(..))` only flag it makes sense to enable the flag by default. 

There was one missing `MACOS_AARCH64_ONLY(ThreadWXEnable __wx(WXWrite, thread));` to make all tests (tier1-7) pass.

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

Commit messages:
 - Update jfrIntrinsics.cpp
 - JDK-8329748: Change default value of AssertWXAtThreadSync to true

Changes: https://git.openjdk.org/jdk/pull/19102/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19102&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8329748
  Stats: 3 lines in 2 files changed: 1 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/19102.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19102/head:pull/19102

PR: https://git.openjdk.org/jdk/pull/19102