Change CI template linter textarea with Ace Editor

Closes #24179 and #19701

See merge request !8452

Use #parts instead of #part to read all the parts of the Message.

Closes #26463

See merge request !8507

Make play button on Pipelines page accessible via keyboard

See merge request !8496

Resolve "Certain buttons are not accessible via the keyboard (Web)"

Closes #26238

See merge request !8469

View spec for Ryancharris/gitlab milestone counter number with delimiter

See merge request !8482

Made download artifacts button accessible via keyboard

Closes #26446

See merge request !8493

Looks like I was accidentally using #part which was adding an extra
empty Mime section

Fix Double Spaced CI Log

Closes #19086

See merge request !8349

Make successful pipeline emails off for watchers

Closes #24845

See merge request !8176

Log LDAP blocking/unblocking events to application log

See merge request !8042

Don't instrument 405 Grape calls

Closes #26051

See merge request !8445

Added update guides for 8.16RC1

See merge request !8502

Re-order update steps in the 8.14 -> 8.15 upgrade guide

Closes #26014

See merge request !8287

Record and show last used date of SSH Keys

See merge request !8113

Fix broken url on group avatar

Closes #26452

See merge request !8464

Fixes #26051.
Signed-off-by: Rémy Coutable <remy@rymai.me>

1. Gems need to be installed before we can run the
  gitlab:workhorse:install task
1. Update gitlab-shell after gitlab-workhorse since it's a manual step
  that needs to be done in `/home/git/gitlab-shell`
Signed-off-by: Rémy Coutable <remy@rymai.me>

Addresses: Issue #13810

1. Adds a last_used_at attribute to the Key table/model
2. Update a key's last_used_at whenever it gets used
3. Display how long ago an ssh key was last used

Fix dead link in Reply by email documentation

Closes #26247

See merge request !8474

Add label to Environments "Date Created" column

Closes #25371

See merge request !8376

Moved the members and groups to single option called members

Closes #25985

See merge request !8281

Adds CHANGELOG entry

Adds MR ID to CHANGELOG entry

Re-add Google Cloud Storage as a backup strategy

Closes #26362

See merge request !8481

Improve UX copy docs on capitalization and punctuation

See merge request !8439

Signed-off-by: Rémy Coutable <remy@rymai.me>

Fixed failing markdown button tests

See merge request !8471

Fixed edit form authenticity_token call failing the tests

See merge request !8472

[ci skip]

With Gitea v1.0.0, notes are imported

See merge request !8298

Added animations to issue boards

Closes #25630

See merge request !8417

Fixed padding and margins for the dropdowns on the members section

Precompile all frontend test fixtures

Closes #26226

See merge request !8384