- store the assoc ID of a UE at the RRC
- if F1 receives an SCTP shutdown, it removes the endpoint
- F1 will also send an "F1 Lost Connection" message to the RRC
- it is not yet possible to reconnect a DU after it had already been
  connected at the CU, since the CU F1AP task will try to rebind GTP,
  which fails

- Free the memory
- for NGAP NAS UL and NAS First request, allocate memory to avoid
  use-after-free errors

- Forward UE capabilities in F1 handlers
- Store at MAC
- Update CellGroupConfig with UE Capabilities of the UE

- MAC creates CellGroupConfig and sends to RRC
- the RRC does not manually update the CellGroupConfig
- MAC handles the RRC processing timer

In this commit, any updates to the CellGroupConfig previously done at
the RRC don't work. In other words, MIMO etc don't work; this is
implemented in the next commit.

Note that the change to take out spCellConfig during reestablishment is
because after reestablishment, as per spec (38.331 5.3.7.2), the UE
should drop the spCellConfig, which we generate by default on the first
UE connection.

Furthermore, add a new variable apply_cellgroup to signal if, after RRC
processing timer, we wish to apply the CellGroup. In some situations,
e.g., Msg.4 ack, we do not want to apply the CellGroup, because for
instance in reestablishment, we await for a reconfiguration of cellgroup
that would be triggered too early.

In NSA case: do not send SIB1

!SIB1 is not correctly filled! This commit does not work with COTS UEs!
The next commit fixes this.

- Move radio config (e.g., minRXTXTIME, SIB1 TDA, do_SRS, etc) down to
  MAC.
- Some parameters in MAC are redundant: delete them.
- Remove call to nr_mac_config_scc() from RRC and simulators, the MAC
  initialization routine calls it implicitly

Previously, filling of F1 Setup Request depended on reading the RRC;
hence, for timing reasons, we only initialized and sent the F1 Setup
Request once the MAC and RRC are ready.

After moving SCC, SCD, MIB, and SIB1 to MAC, the MAC does not depend on
an RRC being present anymore, and hence, the F1 Setup Request does
neither. In this commit, we read the F1 Setup Request after initializing
the MAC.

The SystemInformationBlock 1 is handled at the DU and sent to the CU in
the F1 Setup Request. Hence, move it down to the MAC.

The MasterInformationBlock is handled at the DU and sent to the CU in
the F1 Setup Response. Hence, move it down to the MAC. Furthermore:

- Change type because MIB_PDU_t is 4G type
- Simplify schedule_nr_mib()

As with the ServingCellConfigCommon, the ServingCellConfigDedicated is a
radio-related structure to be handled at the DU.

Note: the reestablishment is broken, and a later commit fixes it.

The ServingCellConfigCommon is an inherently radio-related
configuration. As such, it should be handled by the DU, not the CU.
Therefore, move it "down" to the MAC.

The PCI is given to the CU from the DU in the F1 Setup Request message.
It is a part of the DU, so move it "down".

The F1 Setup Response contains the cell(s) to activate. Hence, prevent
the radio from starting by waiting for the F1 Setup Response before
continuing.

- send F1 Setup using callback
- store f1 setup req locally for reference
- check F1 Setup Req against RRC data structures:
  * if matches: send F1 Setup Response using callback
  * if not matching: send F1 Setup Failure using callback
- don't send CU config update by default, we don't need this
- if the Setup Response does not contain a cell, don't activate. It is
  possible the CU sends a gNB-CU configuration update, which will
  initialize the structures

Use a struct to initialize the RRC at the beginning, and remove the
NRRRC_CONFIGURATION_REQ. This message is not necessary; the RRC/CU
should be initialized from the F1 Setup Request, coming from the DU.

Before this commit, we did not read the ServingCellConfigCommon (SCC)
completely at start; rather, we read most (but not all) of it, then also
the minRXTXTIME, and at RRC initialization in
openair_rrc_gNB_configuration(), we filled the
pusch-TimeDomainAllocationList into the SCC, depending on the
minRXTXTIME.

The reason might be that we read part of the SCC, use that to fill the
NRRRC_CONFIGURATION_REQ, read also the minRXTXTIME (part of the RRC
config), and then we have all we need to "finalize the SCC". Since we
move everything to the MAC, I avoid too much upfront code changes,
hardcode the minRXTXTIME (and check with an assert), and undo this in a
later commit when the "RRC config" relevant for radio parameters, e.g.,
minRXTXTIME, is moved to MAC.

I verified the equality of the SCC before (at the end
openair_rrc_gNB_configuration()) and after (at the end of
get_scc_config()) this commit manually using a printf, assuming that
after RRC initialization, we didn't do any further modifications to the
SCC.  But in fact, I cannot know that we don't do it...

- Simplify code by reading the SCC in a separate function
- Fill the F1 Setup Request message correctly in case of FDD, from SCC