[Transform] refactor cat transform to show more useful information

[hendrikmuhs]

Refactoring of cat transform to show more relevant information. The current cat transform shows a lot of configuration details, however cat should show operationally useful information. This PR changes the defaults.

before:

id create_time              version source_index            dest_index pipeline description transform_type frequency max_page_search_size docs_per_second   state
t1 2020-12-15T16:00:37.783Z 7.11.0  kibana_sample_data_logs t1                              batch          1m        500                  -               STOPPED

after:

id   state checkpoint documents_processed checkpoint_progress changes_last_detection_time
t1 started 19         2309                                    Tue Dec 15 17:12:29 CET 2020
t2 stopped 1          13059               100.00              Tue Dec 15 15:21:00 CET 2020
t4 stopped 1          4654569             100.00              Tue Dec 15 15:58:30 CET 2020
t5 stopped 1          4654569             100.00              Tue Dec 15 16:22:25 CET 2020

Todo:

• document breaking change for 7.12

[elasticmachine]

Pinging @elastic/ml-core (:ml/Transform)

[benwtrent]

I like it. Gives a nicer overview of the current state of things at a glance while still allowing users to get specific info if desired.

[hendrikmuhs]

run elasticsearch-ci/2

[hendrikmuhs]

#66718 proposes a new field in stats, if accepted it makes sense to add this field to cat _transforms, therefore this PR is on hold until #66718 got decided

[hendrikmuhs]

replaced by #68232