VS: Assorted QuickInfo improvements

[majocha]

Replace awful ASCII art separator with something more subtle and align icon to top:

Use the built-in nav link functionality that VS now provides, instead of custom. Restore the little tooltip with file name that once was there IIRC.

That was a low hanging fruit. Here are a few more involved things that come to my mind to do as a follow up:

• Render QuickInfo parts in proper order, i.e. icon -> description -> documentation for each ToolTipElement the service provides.
• Provide option to use monospaced / programming font for the main description.
• Expose option to set width: Add optional width parameter to GetToolTip #14891
• Use JoinableTaskFactory and allow user to cancel the hyperlink navigation: There are two codepaths in link navigation, one is instant as it just goes to the range of symbol, the other one is smart but slower as it looks up the implementation. Provide an option to fallback to fast track when the user cancels.
• Do "find usages" on link click, when we are at the symbol definition already (like C# does it).

[T-Gro]

How would the find usages on link click work?
Open the Find References panel and show them here, as if you triggered a search manually?

[majocha]

How would the find usages on link click work? Open the Find References panel and show them here, as if you triggered a search manually?

Ah, I thought I saw this working in a C# project, but can't get it to work now. Yes it just launched the panel for the symbol.
What we do instead is we don't show the link at all if QuickInfo is triggered on a point of definition.
Alternative that came on my mind right now is to make the link go to signature and vice versa, just like F12 works now.