RFR: 8374519: assert((!inside_attrs()) || VMError::is_error_reported()) failed: cannot print tag inside attrs with "-XX:+LogCompilation -XX:-SerializeVMOutput"

[Guanqiang Han]

Please review this change. Thanks!

**Description:**

The compilation logging is written as structured XML through the global xtty. With SerializeVMOutput turned off, multiple threads can write to the same xmlStream concurrently. This allows XML fragments (especially the tag/attribute header state) to interleave, corrupting the xmlStream markup state machine and triggering the inside_attrs() assertion.

**Fix:**

Ensure xtty remains serialized even when -XX:-SerializeVMOutput is specified.

**Test:**

GHA

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Commit messages:
 - fix 8374519

Changes: https://git.openjdk.org/jdk/pull/29337/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29337&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8374519
  Stats: 43 lines in 2 files changed: 40 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/29337.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29337/head:pull/29337

PR: https://git.openjdk.org/jdk/pull/29337