core/rawdb, cmd, ethdb, eth: implement freezer tail deletion (#23954)

* core/rawdb, cmd, ethdb, eth: implement freezer tail deletion

* core/rawdb: address comments from martin and sina

* core/rawdb: fixes cornercase in tail deletion

* core/rawdb: separate metadata into a standalone file

* core/rawdb: remove unused code

* core/rawdb: add random test

* core/rawdb: polish code

* core/rawdb: fsync meta file before manipulating the index

* core/rawdb: fix typo

* core/rawdb: address comments

core/rawdb/table.go

@@ -74,6 +74,12 @@ func (t *table) Ancients() (uint64, error) {
 	return t.db.Ancients()
 }
 
+// Tail is a noop passthrough that just forwards the request to the underlying
+// database.
+func (t *table) Tail() (uint64, error) {
+	return t.db.Tail()
+}
+
 // AncientSize is a noop passthrough that just forwards the request to the underlying
 // database.
 func (t *table) AncientSize(kind string) (uint64, error) {
@@ -89,10 +95,16 @@ func (t *table) ReadAncients(fn func(reader ethdb.AncientReader) error) (err err
 	return t.db.ReadAncients(fn)
 }
 
-// TruncateAncients is a noop passthrough that just forwards the request to the underlying
+// TruncateHead is a noop passthrough that just forwards the request to the underlying
 // database.
-func (t *table) TruncateAncients(items uint64) error {
-	return t.db.TruncateAncients(items)
+func (t *table) TruncateHead(items uint64) error {
+	return t.db.TruncateHead(items)
+}
+
+// TruncateTail is a noop passthrough that just forwards the request to the underlying
+// database.
+func (t *table) TruncateTail(items uint64) error {
+	return t.db.TruncateTail(items)
 }
 
 // Sync is a noop passthrough that just forwards the request to the underlying