This commit adds mac frame util functions to generate acks (both Imm
and Enh acks) from a received frame. These funtions are utils APIs for
platforms which don't provide ack generation.
This commit also introduces compile options for CSL to control the CSL
IE related part.
This commit adds enhanced frame pending feature of Thread 1.2. This
requires the platform radio driver to correctly set frame pending bit
for Data frames and MAC Data Request frames.
`otPlatRadioFrameUpdated()` is declared not to access any state within
OpenThread. However, the current implementation does read the extended
address. This commit moves the AES process into `Mac::TxFrame`, which
is free of `otInstance` and eliminates the current deep callback
stacks when the radio driver wants to process tx AES from interrupt
context.
Li Cao