RFR: 6640: Run spotless and tests as part of the workflow

[Marcus Hirt]

Running the tests on Linux, Mac OS X and Windows. Holding off a bit on the UI-tests for now.

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Commits:
 - d312b938: Want scripts
 - 6c2b8533: Installing core before the formatting check
 - 7158f059: More windows fun
 - 5a0b675e: Fixing windows formatting script
 - b08ef9a3: Adding scripts for checking formatting and running tests
 - 1aea5e6e: Better name
 - 80d352f3: Testing

Changes: https://git.openjdk.java.net/jmc/pull/10/files
 Webrev: https://webrevs.openjdk.java.net/jmc/10/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JMC-6640
  Stats: 106 lines in 8 files changed: 105 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jmc/pull/10.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/10/head:pull/10

PR: https://git.openjdk.java.net/jmc/pull/10