Beginnings of AUTOVACUUM

This commit introduces AUTOVACUUM to Limbo. It introduces the concept of ptrmap pages and also adds some additional instructions that are required to make AUTOVACUUM PRAGMA work

vendored/sqlite3-parser/src/parser/ast/mod.rs

@@ -1655,6 +1655,8 @@ pub type PragmaValue = Expr; // TODO
 #[derive(Clone, Debug, PartialEq, Eq, EnumIter, EnumString, strum::Display)]
 #[strum(serialize_all = "snake_case")]
 pub enum PragmaName {
+    /// set the autovacuum mode
+    AutoVacuum,
     /// `cache_size` pragma
     CacheSize,
     /// `journal_mode` pragma