[jdk21u] RFR: 8319339: Internal error on spurious markup in a hybrid snippet

[Pavel Rappo]

Please review this backport of JDK-8319339 ([c9077b8b](https://github.com/openjdk/jdk/commit/c9077b8b816d2efe4559c71341228a8dc319604f)) to jdk21u.

This backport is not clean because of [e51472e9](https://github.com/openjdk/jdk/commit/e51472e9a857451451d6df37588bd67f63bc2032), which is absent in jdk21u, but does not need to be backported. The conflict was simple and easily resolved.

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Commit messages:
 - Backport c9077b8b816d2efe4559c71341228a8dc319604f

Changes: https://git.openjdk.org/jdk21u/pull/354/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u&pr=354&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319339
  Stats: 144 lines in 3 files changed: 134 ins; 0 del; 10 mod
  Patch: https://git.openjdk.org/jdk21u/pull/354.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/354/head:pull/354

PR: https://git.openjdk.org/jdk21u/pull/354