[tmva][sofie] Add TopK operator

[lmoneta]

This Pull request adds the support for TopK operator in SOFIE

Implementation provided by GSOC student from Vedant Mehra.

This PR is based on #15837 and should be merged after that one and eventually rebased

[github-actions[bot]]

Test Results

    13 files      13 suites   2d 13h 35m 1s :stopwatch:  2 650 tests  2 649 :white_check_mark: 0 :zzz: 1 :x: 32 634 runs  32 633 :white_check_mark: 0 :zzz: 1 :x:

For more details on these failures, see this check.

Results for commit 449baf17.

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

[ferdymercury]

Superseded by https://github.com/root-project/root/pull/16313