Perform the mirror step in a batch

[laeubi]

Currently the Mirroring is performing each step independently this can lead to considerable slow down as for example the SimpleArtifactRepository performs a save on every adding of a descriptor.

This wraps the mirror step and update of properties into a batch operation to increase performance.

[github-actions[bot]]

Test Results

       9 files  ±0         9 suites  ±0   30m 32s :stopwatch: - 3m 53s 2 181 tests ±0  2 177 :heavy_check_mark: ±0    4 :zzz: ±0  0 :x: ±0  6 633 runs  ±0  6 622 :heavy_check_mark: ±0  11 :zzz: ±0  0 :x: ±0 

Results for commit e1849281. ± Comparison against base commit a795c7f4.

[laeubi]

@merks It seems that I can't find usages of Mirroring beside MirrorApplication but maybe Oomph is using that somewhere?

[merks]

It looks like Oomph only uses that in a test like:

      Mirroring mirror = new Mirroring(sourceRepository, targetRepository, true);
      mirror.setCompare(false);
      mirror.setTransport(transport);
      mirror.setArtifactKeys(keys.toArray(new IArtifactKey[keys.size()]));

      IStatus result = mirror.run(true, false);
      P2CorePlugin.INSTANCE.coreException(result);