New issue shortcut doesnt work on some pages

## What does this MR do?

1. Slightly tidies dispatcher switch case by utilising 'fall through' cases.
2. Adds shortcuts to project pipelines, milestones, builds and forks pages

## Are there points in the code the reviewer needs to double check?

I have a feeling that these may have been missed out of the case statements on purpose?

## Why was this MR needed?

Possible UX issue highlighted in #17929.

## What are the relevant issue numbers?

Closes #17929.

Closes #12616. (dup)

Closes #18123. (dup)

Closes #13688. (dup)

## Screenshots (if relevant)

See merge request !4393