RFR: 7903499: Update various versions used by jtreg's IDEA plugin

[Christoph]

This enables building the plugin with never java versions

I tested with IntelliJ 2023.1.2 and java 17 and 19

Plugin still works

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

Commit messages:
 - update to 7.6.1 and add checkstum
 - update plugin version to latest
 - fix typo
 - Merge remote-tracking branch 'upstream/master' into updateJtregGradlePlugin
 - change path back to default
 - Update plugin for intellij 2023

Changes: https://git.openjdk.org/jtreg/pull/157/files
 Webrev: https://webrevs.openjdk.org/?repo=jtreg&pr=157&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903499
  Stats: 227 lines in 7 files changed: 109 ins; 43 del; 75 mod
  Patch: https://git.openjdk.org/jtreg/pull/157.diff
  Fetch: git fetch https://git.openjdk.org/jtreg.git pull/157/head:pull/157

PR: https://git.openjdk.org/jtreg/pull/157