Use zig-lsp-codegen (#850)

* add lsp.zig

* change references from types.zig to lsp.zig

* remove types.zig and requests.zig

* add tres as a submodule

* transition codebase from types.zig to lsp.zig

* update lsp.zig

* completely overhaul message handler

* fix memory errors

* partially transition tests to lsp.zig

* update lsp.zig

* more test fixes

* disable failing tests

* fix message handling bugs

* fix remaining tests

* access correct union in diff.applyTextEdits

* more message handler fixes

* run zig fmt

* update tres submodule

* fix memory access to freed memory

* simplify initialize_msg for testing

* check if publishDiagnostics is supported

.gitmodules

@@ -4,3 +4,6 @@
 [submodule "src/tracy"]
 	path = src/tracy
 	url = https://github.com/wolfpld/tracy
+[submodule "src/tres"]
+	path = src/tres
+	url = https://github.com/ziglibs/tres.git