feat(1329): System table for system variables

Closes #1329.

Used to persist global parameters for slow query logging and cardinality limits.

crates/core/src/config.rs

@@ -1,5 +1,5 @@
 use crate::util::slow::SlowQueryConfig;
-use spacetimedb_sats::relation::{Column, FieldName, Header};
+use spacetimedb_lib::relation::{Column, FieldName, Header};
 use spacetimedb_sats::{product, AlgebraicType, AlgebraicValue};
 use spacetimedb_vm::errors::{ConfigError, ErrorVm};
 use spacetimedb_vm::relation::MemTable;

crates/core/src/db/datastore/locking_tx_datastore/committed_state.rs

@@ -12,7 +12,7 @@ use crate::{
                 SystemTable, ST_CLIENTS_ID, ST_CLIENT_IDX, ST_COLUMNS_ID, ST_COLUMNS_IDX, ST_COLUMNS_NAME,
                 ST_CONSTRAINTS_ID, ST_CONSTRAINTS_IDX, ST_CONSTRAINTS_NAME, ST_INDEXES_ID, ST_INDEXES_IDX,
                 ST_INDEXES_NAME, ST_MODULE_ID, ST_MODULE_IDX, ST_RESERVED_SEQUENCE_RANGE, ST_SEQUENCES_ID,
-                ST_SEQUENCES_IDX, ST_SEQUENCES_NAME, ST_TABLES_ID, ST_TABLES_IDX,
+                ST_SEQUENCES_IDX, ST_SEQUENCES_NAME, ST_TABLES_ID, ST_TABLES_IDX, ST_VAR_ID, ST_VAR_IDX,
             },
             traits::TxData,
         },
@@ -204,6 +204,8 @@ impl CommittedState {
 
         self.create_table(ST_CLIENTS_ID, schemas[ST_CLIENT_IDX].clone());
 
+        self.create_table(ST_VAR_ID, schemas[ST_VAR_IDX].clone());
+
         // Insert the sequences into `st_sequences`
         let (st_sequences, blob_store) =
             self.get_table_and_blob_store_or_create(ST_SEQUENCES_ID, &schemas[ST_SEQUENCES_IDX]);