[common] simplify mainloop processing

[wgtdkp]

This commit simplifies mainloop process by providing RunMainloop() which encapsulates updating and processing mainloop processores. We also provide BreakMainloop() which can breaks the blocking RunMainloop() method even from another thread.

This commit also enhances mainloop breaking logic to ensure that it can always be stopped immediately by always adding a TaskRunner to the Mainloop processors list.

[codecov[bot]]

Codecov Report

Merging #1110 (80551fa) into main (e5f9183) will increase coverage by 0.12%. The diff coverage is 98.23%.

@@            Coverage Diff             @@
##             main    #1110      +/-   ##
==========================================
+ Coverage   56.53%   56.65%   +0.12%     
==========================================
  Files          85       82       -3     
  Lines        6352     6315      -37     
==========================================
- Hits         3591     3578      -13     
+ Misses       2761     2737      -24     

Impacted Files	Coverage Δ
src/common/task_runner.cpp	70.90% <ø> (+21.78%)	:arrow_up:
tests/unit/test_task_runner.cpp	98.30% <97.18%> (-1.70%)	:arrow_down:
src/agent/main.cpp	70.52% <100.00%> (-1.59%)	:arrow_down:
src/common/mainloop_manager.cpp	100.00% <100.00%> (ø)
src/common/mainloop_manager.hpp	100.00% <100.00%> (ø)
tests/mdns/main.cpp	97.95% <100.00%> (-0.15%)	:arrow_down:
src/mdns/mdns_avahi.cpp	41.91% <0.00%> (ø)
src/mdns/mdns_mdnssd.cpp	22.14% <0.00%> (ø)
... and 7 more

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[wgtdkp]

This PR is obsoleted since the mainloop is already encapsulated in method Application::Run().