[jfx17u] RFR: 8332539: Update libxml2 to 2.12.7

[Johan Vos]

8332539: Update libxml2 to 2.12.7

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

Commit messages:
 - Backport dedcf1d236b5429dcf3c42f5fd1095b28d5da063

Changes: https://git.openjdk.org/jfx17u/pull/192/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx17u&pr=192&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8332539
  Stats: 67 lines in 9 files changed: 26 ins; 9 del; 32 mod
  Patch: https://git.openjdk.org/jfx17u/pull/192.diff
  Fetch: git fetch https://git.openjdk.org/jfx17u.git pull/192/head:pull/192

PR: https://git.openjdk.org/jfx17u/pull/192