Inlay hints

[puremourning]

This is the bare minimum, just forawrding the LSP response, with a few
fixups for ycmd/LSP differences.

---

This change is 

[codecov[bot]]

Codecov Report

Merging #1651 (41a6f95) into master (70a74dc) will decrease coverage by 0.63%. The diff coverage is 45.45%.

:exclamation: Current head 41a6f95 differs from pull request most recent head 6ed8628. Consider uploading reports for the commit 6ed8628 to get more accurate results

@@            Coverage Diff             @@
##           master    #1651      +/-   ##
==========================================
- Coverage   96.11%   95.47%   -0.64%     
==========================================
  Files          90       90              
  Lines        8078     8153      +75     
  Branches      164      164              
==========================================
+ Hits         7764     7784      +20     
- Misses        262      317      +55     
  Partials       52       52              

[mergify[bot]]

Thanks for sending a PR!