[LLVM][UTILS][VSCODE] Add LLVM LSP support in LLVM VS Code extension

[Bertik23]

This PR is part of the LLVM IR LSP server project (RFC)

With this PR we update the current VS Code extension, to support the new LSP server (#161969).

Most of the code and project structure was directly copied from the MLIR VS Code extension with some modifications.
It supports two custom LSP messages llvm/getCfg and llvm/bbLocation that are used for displaying CFGs and cross navigation between the IR and CFG.

[Bertik23]

@yuanfang-chen could you take a look at this? You seem to be the author of the extension
@felipepiovezan you seem to have some experience with the VS Code extension
@River707 you are the author of the MLIR extension if I'm not mistaken, since this is heavily based on it, you might have some insight