Adjust the default trusted_proxies to only include localhost, and allow other trusted proxies to be configured.

Closes #15105

I’ve removed everything related to the feature based on this commit:
ce08f919f34fd8849834365

Resolves #10857.

Fixes #12731

The pattern in the `::reference_pattern` class method in the
ExternalIssue model does not match all valid forms of JIRA project
names. I have updated the regex to match JIRA project names with numbers
and underscores. More information on valid JIRA project names can be
found here:
https://confluence.atlassian.com/jira/changing-the-project-key-format-192534.html

* The first character must be a letter,
* All letters used in the project key must be from the Modern Roman Alphabet and upper case, and
* Only letters, numbers or the underscore character can be used.

ref: https://github.com/ruby/ruby/commit/238b979f1789f95262a267d8df6239806f2859cc

* GITLAB_EMAIL_FROM
* GITLAB_EMAIL_DISPLAY_NAME
* GITLAB_EMAIL_REPLY_TO

If a DB migration occurs, there's a chance that the application settings are
loaded from the cache and provide stale values, causing Error 500s.
This ensures that at startup the settings are always refreshed.

Closes #3643

- Enable CI by default for all new projects

- Offloads uploading to GitLab Workhorse
- Use /authorize request for fast uploading
- Added backup recipes for artifacts
- Support download acceleration using X-Sendfile

[ci skip]