[ntuple] Add FillNoCommit method and RNTupleFillStatus

[hahnjo]

This method can be called instead of Fill if the RNTupleWriter or RNTupleFillContext should not commit the cluster automatically. Instead the calling code must check ShouldCommitCluster() and call it explicitly if necessary.

FYI @makortel this should be the interface that we were discussing some time ago, and should also allow to append multiple RNTuples into a single TFile using parallel writing: The framework must only call FillNoCommit and manually synchronize access to the underlying TFile while explicitly invoking CommitCluster.

[makortel]

FYI @Dr15Jones

[github-actions[bot]]

Test Results

    10 files  ±0      10 suites  ±0   1d 18h 58m 47s :stopwatch: - 4h 49m 51s  2 635 tests ±0   2 635 :white_check_mark: ±0  0 :zzz: ±0  0 :x: ±0  24 868 runs  ±0  24 868 :white_check_mark: ±0  0 :zzz: ±0  0 :x: ±0 

Results for commit 80bda3af. ± Comparison against base commit bf035b88.

:recycle: This comment has been updated with latest results.