refactor(coderd/database): split Time and Now into dbtime package (#9482)

Ref: #9380

coderd/database/types.go

@@ -79,14 +79,3 @@ func (m *StringMap) Scan(src interface{}) error {
 func (m StringMap) Value() (driver.Value, error) {
 	return json.Marshal(m)
 }
-
-// Now returns a standardized timezone used for database resources.
-func Now() time.Time {
-	return Time(time.Now().UTC())
-}
-
-// Time returns a time compatible with Postgres. Postgres only stores dates with
-// microsecond precision.
-func Time(t time.Time) time.Time {
-	return t.Round(time.Microsecond)
-}