Fixes ubsan runtime error.

This is currently not used, but prevents mishaps once such code is written.

This is not currently used, but the absence of the call could cause memory leaks
in the future.

Call sieve_action_execution_pre() just before the first action activity and
always call sieve_action_execution_post() at the end of each action activity.
This makes things clearer and it makes the next commit easier.

lib-sieve: sieve-result - Remove code duplication between implicit keep and normal action execution.

Preparation for next commit.

This will now readily happen when executed (not committed) success implicit keep
is replaced by a failure implicit keep.

Before, actions were executed and committed in full after each script in a
sequence. With this change, actions can still be rolled back until the end of
all Sieve script and action execution.

The committed flag is set when at least one action was committed successfully.
The existing executed flag is repurposed to signal successful execution of at
least one action. These flags are now also properly managed for the keep action.

Allows doing the check in the action finalization function.

It is no longer used.

Adds status parameter to sieve_result_execute().

Makes sure it is consistent for a later commit when action exection is more fragmented.