RFR: 8091: Refactoring for jmc/application

Wed Jun 14 21:24:30 UTC 2023

The sibling PR to #495 for the non-core project.

It cleans up the pom, bumping some versions and fixing URLs.
The integration for spotless and checkstyle is cleaner now, allowing to build projects from subdirectories.
spotless is called as part of the main build lifecycle now.

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Commit messages:
 - JMC-8091

Changes: https://git.openjdk.org/jmc/pull/497/files
 Webrev: https://webrevs.openjdk.org/?repo=jmc&pr=497&range=00
  Issue: https://bugs.openjdk.org/browse/JMC-8091
  Stats: 1879 lines in 146 files changed: 69 ins; 213 del; 1597 mod
  Patch: https://git.openjdk.org/jmc/pull/497.diff
  Fetch: git fetch https://git.openjdk.org/jmc.git pull/497/head:pull/497

PR: https://git.openjdk.org/jmc/pull/497