Resolve "Navigation - Move contextual navigation to sidebar"

Closes #34023

See merge request !12470

Backport inline prop on loading_icon from EE

See merge request !12490

Refactor emoji helpers in preparation for async loading

See merge request !12432

[ci skip]

Ignore JSON files generated from PO files

See merge request !12329

Fix head pipeline stored in merge request for external pipelines

Closes #34130

See merge request !12478

[ci skip]

Update mmap2 gem to fix missing symbol error that happens on some installations from source

Closes #34221

See merge request !12492

Make the SimpleExecutor rescue exceptions in the executing Checks

See merge request !12487

Update mmap2 gem tha disables mmap_obj.gsub! as current implementation uses method that is no longer part of Ruby API

See
https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/2246#note_33577729

ruby 2.4 compat: update to webmock 2.3.2

See merge request !12471

Update templates for 9.3

See merge request !12461

Update dependencies list for 9.3

See merge request !12462

Fix application error when Project#last_activity_at is nil

Closes #34276

See merge request !12443

Slightly refactor pipeline schedules form in preparation for additions

See merge request !12134