chore: add custom libpg_query binding (#465)

brings home the custom binding that was experimented in pg_parse.

no functional changes, just different imports and a bit of cleanup.

also removes the libpg_query submodule - we are now cloning the repo
"live" in the build script.

closes #453

Author: psteinroe

.gitmodules

@@ -1,7 +1,3 @@
-[submodule "libpg_query"]
-	path = libpg_query
-	url = https://github.com/pganalyze/libpg_query.git
-    branch = 17-latest
 [submodule "crates/tree_sitter_sql/tree-sitter-sql"]
 	path = lib/tree_sitter_sql/tree-sitter-sql
 	url = https://github.com/DerekStride/tree-sitter-sql