Autolabel group label on MRs based on author group information from team.yml

This MR changes the following:

1. Adds a new pre-hygiene job label-merge-request-author-group to label MR based on author's group
2. The label inference in stage-and-group-labels-hygiene for Merge Request is updated to follow the following table, in order to account for MR author's group. The rows marked with * are new behaviour introduced in this MR. Others follow the status quo.

#	has_stage_label?	has_group_label?	has_category_labels?	group_is_part_of_stage?	inference_strategy
1	true	true	true	N.A	Not needed
2	true	true	false	true	infer category from group
3 *	true	true	false	false	do not infer category
4	true	false	true	N.A	infer group from stage
5	true	false	false	N.A	infer group from stage
6 *	false	true	true	N.A	do not infer stage
7 *	false	true	false	N.A	do not infer stage and category
8	false	false	true	N.A	do not infer stage and group
9	false	false	false	N.A	Not possible

Caveat:

• MRs that have legacy team labels (with [DEPRECATED]) would follow the status quo inference which uses the legacy team labels.

✅ Dry run default-labels scheduled pipeline https://gitlab.com/gitlab-org/quality/triage-ops/pipelines/114386031

✅ Schedule-sync dry run https://gitlab.com/gitlab-org/quality/triage-ops/-/jobs/423438961:

✅ Dry run policies/stages/pre-hygiene/label-merge-request-author-group.yml on gitlab-org https://gitlab.com/gitlab-org/quality/triage-ops/-/jobs/423438974 result looks good.

For reference and comparison, status quo default-labels pipeline: https://gitlab.com/gitlab-org/quality/triage-ops/pipelines/114388839

Follow up issues:

• ✅ #402 (closed) Comment if MR author group cannot be determined !390 (comment 278719721)

Consider adding documentation to the handbook pages for Triage Operations when creating a new triage policy or triage package:

• https://gitlab.com/gitlab-com/www-gitlab-com/blob/master/source/handbook/engineering/quality/triage-operations/index.html.md

Closes #141 (closed)