[EGD-5737] Merge master into experimental

Keep experimental up to date with changes from master

[EGD-5737] Merge master into experimental

Keep experimental up to date with changes from master

[EGD-5737] Merge master into experimental

Keep experimental up to date with changes from master

[EGD-5090] Add Brownout GUI window

Gui window will appear due to brownout
event. System shutdown will be also called.

[EGD-5325] Remove using namespace directives from headers

"Using namespace" directive should not be added in headers
because this practice pollutes source files.

[EGD-5155] Change Timers debug functionality

Enhanced Timers debug functionality.

Merge branch 'master' into stable

[EGD-2501] Add gsm powerdown due to battery

Gsm model power state maintenance based on battery level.

[EGD-5086] Fix voice not starting when calling

Due to a race condition between source and sink voice is not always
starting when calling. Introduce audio stream connections to avoid
race condition and improve handling of audio start and stop operations.

Signed-off-by: Marcin Smoczyński <smoczynski.marcin@gmail.com>

[EGD-5186] Change minimum CPU frequency to 132 MHz

Temporary minimum CPU frequency limitation

[EGD-4887] Add PLL2 clock switching

Pll2 will be disabled at the lowest CPU frequency,
which will save power

[EGD-5133] Fix settings bus add duplications

Changed Bus Channels vector to set to prevent
duplicates and cleaned logging.

[EGD-5151] Fix timers callback issue

Fix timers callbacked issue and make sure there is no need to
call connect() after each stop().

[EGD-4881] Add oscillator clock switching mechanisms

Osc will change automatically at the lowest CPU frequency,
which will save power

[EGD-5050] Add brownout detection

Brownout detectection realized through charger driver

[EGD-4694] Add CPU frequency shift mechanism

The CPU frequency changes automatically which saves energy

[EGD-4952] Fixes for rt1051

[EGD-4952] Added critical level check + messages

[EGD-4696] Several stabilization patches. (#1192)

Merge branch 'master' into stable