[llvm] [mlir] [LLVM][MLIR] Move LSP server support library from MLIR into LLVM (PR #157885)

[Jan Ječmen via llvm-commits]

JanJecmen wrote:

This is the json that is sent to the lsp server:
```
{"jsonrpc":"2.0","id":1,"method":"pdll/viewOutput","params":{
  "uri":"test:///foo.pdll",
  "kind":"ast"
}}
```
and it should find the uri in the params object but somehow doesn't. Wondering if root is the top-level object or the params.

But in any case, I don't understand how this patch could cause this. I must be missing something...

https://github.com/llvm/llvm-project/pull/157885