Rename PostgresScanTableFunction

Because this can conflict with DuckDB's `postgres` extension which check scanner by name eg. https://github.com/duckdb/duckdb-postgres/blob/8461ed8b6f726564934e9c831cdc88d431e3148f/src/storage/postgres_insert.cpp#L193-L195

src/scan/postgres_scan.cpp

@@ -203,7 +203,7 @@ PostgresScanFunctionData::~PostgresScanFunctionData() {
 //
 
 PostgresScanTableFunction::PostgresScanTableFunction()
-    : TableFunction("postgres_scan", {}, PostgresScanFunction, nullptr, PostgresScanInitGlobal, PostgresScanInitLocal) {
+    : TableFunction("pgduckdb_postgres_scan", {}, PostgresScanFunction, nullptr, PostgresScanInitGlobal, PostgresScanInitLocal) {
 	named_parameters["cardinality"] = duckdb::LogicalType::UBIGINT;
 	named_parameters["relid"] = duckdb::LogicalType::UINTEGER;
 	named_parameters["snapshot"] = duckdb::LogicalType::POINTER;