[jdk21] RFR: 8310861: Improve location reporting for javac serial lint warnings [v2]

[Joe Darcy]

> Backport to JDK 21.

Joe Darcy has updated the pull request incrementally with one additional commit since the last revision:

  Add missing file.

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

Changes:
  - all: https://git.openjdk.org/jdk21/pull/63/files
  - new: https://git.openjdk.org/jdk21/pull/63/files/f151e9a9..ccc350f2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk21&pr=63&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk21&pr=63&range=00-01

  Stats: 0 lines in 1 file changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk21/pull/63.diff
  Fetch: git fetch https://git.openjdk.org/jdk21.git pull/63/head:pull/63

PR: https://git.openjdk.org/jdk21/pull/63