#### Why I did it
To fix the timezone sync issue between the containers and the host. If a certain timezone has been configured on the host (SONIC) then the expectation is to reflect the same across all the containers.
This will fix [Issue:13046](https://github.com/sonic-net/sonic-buildimage/issues/13046).
For instance, a PST timezone has been set on the host and if the user checks the link flap logs (inside the FRR), it shows the UTC timestamp. Ideally, it should be PST.
Linkmgrd monitors link status, mux status, and link state. Has
the link becomes unhealthy, linkmgrd will trigger mux switchover
on a standby ToR ensuring uninterrupted service to servers/blades.
This PR is initial implementation of linkmgrd.
Also, docker-mux container hold packages related to maintaining and managing
mux cable. It currently runs linkmgrd binary that monitor and switches
the mux if needed.
This PR also introduces mux-container and starts linkmgrd as startup when
build is configured with INCLUDE_MUX=y
Edit: linkmgrd PR will follow.
signed-off-by: Tamer Ahmed <tamer.ahmed@microsoft.com>
Related work items: #2315, #3146150
