[CALCITE-7751] Skipped CI jobs when adding labels

[zabetak]

Jira Link

CALCITE-7751

Changes Proposed

1. Split CI jobs requiring labels in its own workflow file.
2. Remove skip logic based on labels from main.yml.

[zabetak]

I added the LGTM label immediately to test that jobs are not going to be skipped.

[zabetak]

As expected the Slow Tests job was skipped since the appropriate label is missing.

[zabetak]

Just added the "slow-tests-needed" label and the respective action started running leaving all the rest untouched.

[xiedeyantu]

LGTM!
I like this change!

[xiedeyantu]

Just added the "slow-tests-needed" label and the respective action started running leaving all the rest untouched.

Exactly as expected — I just happened to see this trigger effect!

[mihaibudiu]

YAML+github actions is one of these things which I never put an effort to learn (it's really a top contender to the title of the "Worst language ever designed"), so I can't review this myself.
It's great if it does solve the problem.

[snuyanzin]

since you touched this: I wonder if we need to use newer checkout action...