[LS] Implement "Go To Definition" for dependencies

[jribbink]

Issue to be solved

It would be very useful if the LS implemented "Go to Definition" for dependencies.

Suggested Solution

• Implement "Go To Definition" for "real"/local file dependencies (straightforward)
• Implement "Go To Definition" for "virtual"/internal dependencies such as Crypto, Account, others (maybe harder, this unfortunately may require Extension Host integration for a virtual filesystem, but should be possible if some APIs can be served by the LS)