Improve Keyboard shortcut help screen

What does this MR do?

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/65367

Ported to EE in https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/15102 due to ee_compat failing on the gitlab.pot file.

Improves the help screen within GitLab that shows what the keyboard shortcuts are.

Adds:

• Missing Epic shortcuts
• Missing releases shortcut
• Editing shortcuts section

Removes:

• Unnecessary (show more) link. All the shortcuts should be visible, since it was just bare whitespace when they were hidding.

Combines:

• Issues and Merge requests into one section.
• Finding Project File, Project Files browsing, Project File into one section.

Changes:

• Network Graph is now known as Repository Graph
• Reorders items based on their location in the UI, and groups related items together.

Before / After

For reference, this is how it looks with the (Show All) link. Just wasting the whitespace. Might as well show all the shortcuts, like above:

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry for user-facing changes, or community contribution. Check the link for other scenarios.
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance and testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team