RFR: 8091: Refactoring for jmc/application [v2]

[Christoph Langer]

> 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.

Christoph Langer has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains one commit:

  JMC-8091

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Changes: https://git.openjdk.org/jmc/pull/497/files
 Webrev: https://webrevs.openjdk.org/?repo=jmc&pr=497&range=01
  Stats: 1874 lines in 146 files changed: 69 ins; 210 del; 1595 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