Fix duplicate function entries in the catalog

[scsmithr]

Description

Currently we're inserting multiple functions with the same name due to the entry generation not accounting for our namespace rules here:

glaredb/crates/sqlbuiltins/src/functions/mod.rs

Lines 194 to 222 in 608cc71

	let udfs = udfs
	.into_iter()
	.flat_map(|f| {
	let entry = (f.name().to_string(), f.clone());
	// TODO: This is very weird to do here as this completely
	// bypasses our schema resolution. It also results in duplicate
	// function entries with the same name as the function's `name`
	// argument is not aware of the namespace being added here.
	match f.namespace() {
	// we register the function under both the namespaced entry and the normal entry
	// e.g. select foo.my_function() or select my_function()
	FunctionNamespace::Optional(namespace) => {
	let namespaced_entry = (format!("{}.{}", namespace, f.name()), f.clone());
	vec![entry, namespaced_entry]
	}
	// we only register the function under the namespaced entry
	// e.g. select foo.my_function()
	FunctionNamespace::Required(namespace) => {
	let namespaced_entry = (format!("{}.{}", namespace, f.name()), f.clone());
	vec![namespaced_entry]
	}
	// we only register the function under the normal entry
	// e.g. select my_function()
	FunctionNamespace::None => {
	vec![entry]
	}
	}
	})
	.collect::<HashMap<_, _>>();

Closing this issue requires this test to pass:

glaredb/crates/metastore/src/database.rs

Lines 1409 to 1435 in 608cc71

	#[test]
	fn builtin_catalog_no_function_name_duplicates() {
	// TODO: Fix this
	// Ensures each function is a unique (schema, name) pair.
	// let catalog = BuiltinCatalog::new().unwrap();
	// let names: Vec<(u32, &String)> = catalog
	// .entries
	// .values()
	// .filter_map(|ent| match ent {
	// CatalogEntry::Function(ent) => Some((ent.meta.parent, &ent.meta.name)),
	// _ => None,
	// })
	// .collect();
	// let mut deduped: HashSet<_> = names.clone().into_iter().collect();
	// let diff: Vec<_> = names
	// .into_iter()
	// .filter(|name_and_parent| {
	// let was_present = deduped.remove(name_and_parent);
	// !was_present // We saw this value before, indicates a duplicated name.
	// })
	// .collect();
	// assert_eq!(Vec::<(u32, &String)>::new(), diff);
	}