Fix over-nesting of artifacts object store settings

Closes #2640

See merge request !1816

Added support for idle_in_transaction_session_timeout

Closes gitlab-com/infrastructure#2345

See merge request !1812

Change maintainer to 'GitLab, Inc.' in line with signing key

See merge request !1821

Organize methods in Build class

Closes #2626 and #2645

See merge request !1807

Resolve "Mattermost does not remember teamname display settings from gitlab.rb on update."

Closes #2643

See merge request !1813

Change signing key name

See merge request !1818

With #2632, we generated a new key, and it is now under a different name. Update `.gitlab-ci.yml` to change this.

This adds support for the PostgreSQL setting
"idle_in_transaction_session_timeout", which is new in PostgreSQL 9.6.
This setting can be used to control the time a transaction is allowed to
remain in the state "idle in transaction".

Fixing typo in runit_service specs

See merge request !1815

Add Prometheus client after_fork hook to reset file backed metrics

Closes gitlab-ce#35588

See merge request !1811

Build and configure gitaly-ruby

See merge request !1798

Fix LDAP SSL ca_file config key

See merge request !1810

Update smtp.md

See merge request !1809

Updating GitLab Mattermost to 4.0.2 for GitLab 9.4.X release

See merge request !1808

Add a deprecation note in Omnibus MySQL support

Closes #2593

See merge request !1756

Added Dinahosting to SMTP configuration

Prune Makefile by converting targets to rake tasks

Closes #1677

See merge request !1722

I accidentially left the `echo` in place from debugging this script. We then somehow missed that it was still present in the review.

Closes #2627