Navigate to Prototypes from hover overlay

[cesrjimenez]

We are working towards displaying prototype code intelligence in addition to definitions, references, and implementations. I'll be adding the PR with the work here shortly.

However we don't have a way to see them from the hover popup.

Adding a fourth button for prototypes will feel too crowded. As such, @olafurpg suggests we mirror something similar to how JetBrains UI.

• Add some kind of triple dot ... menu in the popover for implementations/prototype similar to JetBrains (see screenshot)

• Add keyboard shortcut for implementations/prototypes/references

• Add up/down arrow icons in the gutter similar to JetBrains. These should only appear at the definition site.

[camdencheek]

Related to https://github.com/sourcegraph/sourcegraph/issues/60428. Maybe another point towards a context menu