Feature request: try_update

Like try_insert except it's try_update:

// Pseudocode
bool try_update(ctx, primary_key_value, value):
  if ctx.primary_key_column.try_find(primary_key_value):
    // Row with a matching primary key column exists
    ctx.primary_key_column.delete(primary_key_value)
    ctx.primary_key_column.insert(primary_key_value, value)
  else:
    // The row with the matching primary key didn't exist
    return false