Fixes quick actions add label when adding a label which name middle
word overlaps with another label name: for example adding "A B C" when
also label "B" exists.
With the fix only the label "A B C" is correctly added, previously
also the label "B" was added due to the middle word overlaps.

* Extend quick actions dsl to allow specifying model types
to which given quick action applies
* Rename issuable attribute to noteable in interpret_service.rb
* Refactor and reorder quick action specs
* Create a shared example spec for each quick action to be used for
issue, merge request and commit specs.

https://gitlab.com/gitlab-org/gitlab-ce/issues/50199

Fix 'commands applied' messages not being shown when issue is promoted to epic
using slash commands.

Add support for group entities to quick actions

With this quick action the user can create a new MR starting from
the current issue using as `source_branch` the given `branch name` and
as `target_branch` the project default branch. If the `branch name` is
omitted a name is automatically created starting from the issue title.

Sometimes we don't want to trigger any quick actions that cause side
effects. For example when building a record to validate. This allows
listing the quick actions that need to be performed.