[clangd] Improve hover on arguments to function call

Summary:
In cases like:
  foo(a, ^b);
We now additionally show the name and type of the parameter to foo that
corresponds that "b" is passed as.

The name should help with understanding what it's used for and type can
be useful to find out if call to foo() can mutate variable "b" or not
(i.e. if it is pass by value, reference, const reference, etc).

Patch By: adamcz@ !

Reviewers: kadircet

Reviewed By: kadircet

Subscribers: nridge, ilya-biryukov, MaskRay, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D81169