[relay-lsp] Support go to definition for arguments #7005

Job	Run time
JS Tests (Node 14.x)	1m 28s
VSCode Extension Lint	18s
JS Tests (Node 16.x)	1m 37s
Compiler output check (ubuntu-latest)	4m 25s
Build Rust Compiler (ubuntu-latest)	4m 10s
Compiler output check (macos-latest)	5m 48s
Build Rust Compiler (ubuntu-latest)	5m 21s
Rust Tests (ubuntu-latest)	5m 16s
Build Rust Compiler (macos-latest)	4m 10s
Rust Tests (macos-latest)	7m 38s
Build Rust Compiler (macos-latest)	9m 14s
Rust Lint	12s
JS Lint	57s
Rust Tests (windows-latest)	5m 44s
Build Rust Compiler (windows-latest)	6m 14s
Flow Typecheck	38s
Publish to NPM	0s
	1h 3m 10s

Provide feedback