rust-analyzer: Add better support for `TypeHint`s and `ParameterHint`s

[PatOConnor43]

The current rust inlay-hints implementation puts everything at the end of the line when the intended behavior of Type and Parameter hints is to be interspersed in the line. We should be able to draw these hints more closely to this.

Where TypeHints go after variable declarations and ParameterHints are paired with their variables.

Related PRs:
#13
#9

[mvforell]

To my knowledge it is currently not possible to display the hints in other positions than at the end of the line. The hints are added as virtual text which can only be placed after any other text in the line (see the documentation).

[PatOConnor43]

I just read that in the docs too 😅 Well, this may not work how I want it to then 😬

[mvforell]

I guess we'll have to wait until NeoVim supports virtual text in arbitrary positions...

[PatOConnor43]

This PR seems very related as well neovim/neovim#9496

[PatOConnor43]

It also seems like coc-rust-analyzer also only supports ChainingHints for this reason.
fannheyward/coc-rust-analyzer#177 (comment)

[rockerBOO]

#19

This adds support for setting your own options of the hints you want.

require'lsp_extensions'.inlay_hints{ enabled = {"ChainingHint", "TypeHint", "ParameterHint"} } 

[PatOConnor43]

That should be fine. I'll close this.

[univerz]

this workaround looks useful fannheyward/coc-rust-analyzer#394 (comment)