Provide transition duration for ui side dimming

The enabler for ui side dimming was already implemented earlier, but
turns out it does provide enough information and had some glitches.

In addition to fade-to-black -level the signal contains also the
transition duration that ui side should use for the level change.
This allows using mce brightness fading timing configuration also
for the transitions happening at lipstick side.

To avoid unwanted brightness jumps during display power up, the ui
side fading level is retained over display off periods. Whether it
is still needed after display power up is evaluated when als data
becomes available.

Fading by 70% made the display too dark - adjusted to 50%.

[mce] Provide transition duration for ui side dimming. Contributes to JB#18412
Merge pull request #220 from spiiroin/jb18412_ui_side_dimming

Provide transition duration for ui side dimming
Bump mce version to 1.36.6
WIP add fixme notes
WIP turn off optimizations -> better valgrind call stacks
WIP Saturate DBusMessage caching in libdbus to help memory leak analysis

The libdbus keeps a cache DBusMessage objects and recycles them. While
this is good from performance point of view, it also means that some
messages are never released and are attributed in valgrind logs to the
place that happened to do the initial allocation. This makes it difficult
to see if messages are leaked or not.

By creating a number of dummy dbus messages and then releasing them
we can saturate the caching mechanism. After this we can be relatively
sure that DBusMessages are not being leaked as long all of them are
reported to originate from cache stuffing function.
WIP Add datapipe_execute_refcount_triggers() helper function

There are copy-pasted refcount_trigger loops scattered around
the datapipe module. These loops also use g_slist_nth_data()
effectively making O(N) task take O(N^2) time.

Replace inlined copy-paste loops with a call to helper function.
WIP Use single pass datapipe trigger iteration

Caveat: Will break if trigger does self-removal (or the next item)
WIP vebose datapipe init/quit