* first step towards moving MAC timers to stack. Mac is still using its own timers. srslte::timers class can be restructured.
* moved timers out of the UE MAC
this fixes the issue when the stack is torn down if, for example,
the radio couldn't be loaded correctly. it will hence call stop() on all stack
components which are not initialzized yet, and logging therefore doesn't work.
the log object is know during contruction time and therefore can be passed
in as soon as possible.
- add interface to RRC to allow NAS to query the DRB for a given
EPS bearer id
- extend interface for NAS to setup GW to also pass LCID of bearer
- in NAS, use this new interface to pass actual LCID of the default
DRB when creating the TUN device
- abstract UE object now consists of a radio, a PHY, and a stack layer
- add new stack abstraction layer that combines MAC, RLC, RRC, PDCP, NAS and GW
- PHY layer now has a single stack interface and does not talk to MAC and RRC seperatly