Bluetooth: host: Convert bluetooth host to using k_timeout_t struct

Convert bluetooth host to using k_timeout_struct for the timeout values.
This is mostly replacing s32_t with k_timeout_t.
In l2cap the handling of no timeout in send channel request was removed
since the timeout is both documented as minimum of 1 second and never
given any no timeout value.

Signed-off-by: Joakim Andersson <joakim.andersson@nordicsemi.no>