RFR: 8324736: Invalid end positions for EMPTY_STATEMENT

[Archie Cobbs]

In the fix for [JDK-8305671](https://bugs.openjdk.org/browse/JDK-8305671), an `EMPTY_STATEMENT` representing a lone semicolon was being created with the wrong source code position. The bug was that the starting position needed to be captured prior to advancing to the next token, not after.

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Commit messages:
 - Fix bug where source positions got reversed.

Changes: https://git.openjdk.org/jdk/pull/17595/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17595&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8324736
  Stats: 87 lines in 2 files changed: 86 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/17595.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17595/head:pull/17595

PR: https://git.openjdk.org/jdk/pull/17595