Added changelog

This only changes behaviour for masters, as developers are already prevented from updating/deleting tags without the Protected Tags feature

Fixes ProtectedBranches#create flash errors bug due to
typo in 'flash[:alert] = @protected_branches.errors'

This memorized array appears to originally come from https://gitlab.com/gitlab-org/gitlab-ee/commit/19c2c90ccac86a21eb4266b9a5972162f917f692 which has a commit message of ‘fix warnings’. Without any comments on the original pull request I think we can safely get rid of it unless warnings re-appear.

Makes it clear this is only used in dropdowns, instead of cluttering up Project class. Since we only care about branch names, it is also possible to refactor out a lot of the set/reject logic.

A benchmark on Array/Set subtraction favoured using Arrays. This was with 5000 ‘branches’ and 2000 ‘protections’ to ensure a similar comparison to the commit which introduced using Set for intersection.

Comparison:
   array subtraction:      485.8 i/s
     set subtraction:      128.7 i/s - 3.78x slower

ProtectedTagEdit class for edit protected tags

Protected Tags List initializer

Export Protected Tags Editing classes

Initialize Protected Tags Edit functionality

Render Push levels dropdown

Increase dropdown width within Tags list

Update column widths

Uncommented protected tags feature specs copied from protected branches

Should provide basic CRUD backend for frontend to work from. Doesn’t include frontend, API, or the internal API used from gitlab-shell

Added schema.rb for protected tags
Removed unnecessary table ‘protected_tag_merge_access_levels’
Fixed timestamps on protected_tags

Protect tag partial
Apply styles to protected tag same as protected branch
Render protected tags within Project Settings > Repository
Protected Tags Classes
Re-export protected tag classes
Initialize Protected tags feature under Repository Settings page
Update property names for tags
Add protected tags to bundle config

Fix sticking of the database load balancer

See merge request !1502

CE upstream: Tuesday

Closes gitaly#166 and gitaly#168

See merge request !1565

Port of 28732-expandable-folders to EE

See merge request !1538

Allow to edit build minutes per user ee

Closes gitlab-ce#30163

See merge request !1535