Docs: Pages - refactor "Custom domain / SSL" documentation

Closes #47585, #60612, #44606, and #63753

See merge request gitlab-org/gitlab-ce!30363

- Move steps to new doc
- Move all concepts to different docs

Add Namespace#feature_available no-op

Closes #60908

See merge request gitlab-org/gitlab-ce!30641

Resolve "Add size 96 to avatar sizes in avatar.scss"

Closes #64499

See merge request gitlab-org/gitlab-ce!30671

Add a note about implicit Dockerfile serverless runtime

See merge request gitlab-org/gitlab-ce!30672

expand (CD) acronym

See merge request gitlab-org/gitlab-ce!30646

Add example of ENV variables for image and services.

See merge request gitlab-org/gitlab-ce!27320

Verified snippet works with 11.10.1

Rename "discussions" to "threads" in docs

See merge request gitlab-org/gitlab-ce!30037

Filter Geo proxied data from api_json.log

See merge request gitlab-org/gitlab-ce!30687

Currently the base64-encoded value of the push-to-secondary data is
saved in `api_json.log`, and this can easily be hundreds of
megabytes. We should filter this from the logs.

Fix whitespace in user and misc docs

See merge request gitlab-org/gitlab-ce!30605

Many code blocks are 4spaced, and they render in GitLab
without coloring as a result, even though they are
fenced with a language label. If in a list, other items
woll render as being in a code block too, even if not
meant to. This fixes all these issues, and cleans up
minor whitespace issues in /user, /security, /ssh
and /migrate_ci_to_ce docs.

Add more file extentions to file type icon class

See merge request gitlab-org/gitlab-ce!30316

Remove obsolete chaos routes

See merge request gitlab-org/gitlab-ce!30706

Update markdown lint style and option files

See merge request gitlab-org/gitlab-ce!30595

Add commented lines explaining the file, and including
rules that should pass already, and commented out rules
that can be added in the future, for reference.

Remove extra blank lines from docs

See merge request gitlab-org/gitlab-ce!30650

Removing extra blank lines in docs that serve
no purpose, as well as some --- lines that also
are not needed.

Remove deprecated docs sections of Secure jobs

Closes #63739

See merge request gitlab-org/gitlab-ce!30527

Remove trailing whitespace in docs (part 2)

See merge request gitlab-org/gitlab-ce!30649

Remove unneeded trailing whitespace in lines in
/security /workflow /user docs

Single codebase: Remove an extra whitespace in test files

See merge request gitlab-org/gitlab-ce!30710

Partial CE backport of https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/10565Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

Fix typo "beetween" in timeout validation message

See merge request gitlab-org/gitlab-ce!30705

Unquarantine previously failing autodevops spec

Closes gitlab-org/quality/nightly#108

See merge request gitlab-org/gitlab-ce!30691

CE backport of reply button tracker refactor

See merge request gitlab-org/gitlab-ce!28298

create_project_with_auto_devops_spec.rb # runs autodevops
was previous failing

This previously failing test has passed consecutively

Move functions for multiple boards in BoardService to core  (CE-backport)

See merge request gitlab-org/gitlab-ce!30624

(cherry picked from commit 9dbefac95a8b60b93ba7b05fd7bf69b80b395f54)

CE port of "Fix page refresh in retry_until"

See merge request gitlab-org/gitlab-ce!30656

Update lodash to 4.7.14 and lodash.mergewith to 4.6.2

Closes #64416

See merge request gitlab-org/gitlab-ce!30602

Fix Project Badge Buttons

See merge request gitlab-org/gitlab-ce!30678

z-index fixed for diff file dropdown

See merge request gitlab-org/gitlab-ce!30657