Move to Java 17 and higher

[jkosternl]

Refactored mechanism how the EasyDoclet in the unittests was used. Now it uses less internals of the JVM, but uses the Start class of the Javadoc tools. The same tools are used by the Javadoc binary itself, so it is more future proof.

Secondly, bumped a lot of plugins used and deps were available.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (7b90f2d) 84.33% compared to head (8544aa5) 84.31%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #173 +/- ## ============================================ - Coverage 84.33% 84.31% -0.02% Complexity 1390 1390 ============================================ Files 79 79 Lines 4456 4457 +1 Branches 523 523 ============================================ Hits 3758 3758 - Misses 564 565 +1 Partials 134 134 ```

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