RFR: 8329748: Change default value of AssertWXAtThreadSync to true

[Dean Long]

On Mon, 6 May 2024 11:10:08 GMT, Tobias Holenstein <tholenstein at openjdk.org> wrote:

> 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.

Changes requested by dlong (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/19102#pullrequestreview-2041740481