Set ulimit of core to -1 enable core dumps for file-based core dumping.
Note that it is not necessary for e.g., systemd-coredumpd, but put it
for completeness.

- Print problems, e.g., segfault
- Handle signals and zombie processes properly

Some CI users (OAI developers) expressed that the warning of the `docker
volume prune` before starting RFsim is confusing. To avoid the warning in
the HTML, force the removal; if the volume does not exist, no warning is
emitted.

To still catch possible problems, do not do this in the `terminate.xml`
so we might still see if there are other problems.

move command line sample offset and 3/4 sampling option at top level, as it is common option for 4G,5G xNB and UE

add LOG_DDUMP() to dump a buffer in the regular tracing filter system (like PHY, MAC, ...), use it and do simple cleaning (better format)

- improves code readability and maintainability

- centralized channel simulation documentation in channel_simulation.md
- removed redundant documentation repeated in multipled .md files
- updated links
- removed obsolete information
- introduced mermaid flowchart for rfsim
- added missing information about available options and usage
- deleted:    ../../../openair1/SIMULATION/TOOLS/DOC/devusage.md
- deleted:    ../../../openair1/SIMULATION/TOOLS/DOC/rtusage.md
- deleted:    ../../../openair1/SIMULATION/TOOLS/DOC/arch.md

related to issue #739

Ensure that the UE has an IP address before continuing the test.
Otherwise, it might happen we ping before the UE is connected.

Do not do this in do-ra and phytest, as they use --noS1, which implies
statically assigned IP address, so IP address check always succeeds(!).

Make RFsim start up faster by starting core and RAN start at the same
time. This speeds up because we do not wait for "healthy" containers
serially, but parallely.

For the RAN, it is safe to start gNB and UE at the same time in SA mode
(as the UE will only attach once the radio, and hence the full gNB, is
ready).

We do not start in parallel in do-ra and phytest, as in these modes the
gNB first has to write a UE-specific configuration file. If we start
both gNB and UE at the same time, the UE might try to read the file
before it is written, leading to a failure.

- comments to improve readability of the code
- Clang formatting of E1 / RRC (partial)

- new folder dedicated to E1AP docs
- new file to document E1AP procedures

- PDCP reestablishment on CUCP (DRBs) triggering Bearer Context Modification procedures over E1
- Performing PDCP reestablishment for requested DRBs on CUUP
- Introduced function to notify re-establishment to CU-UP
- removed call to PDCP reestablishment for the DRBs on CUCP (it's done on CUUP)

cuup_notify_reestablishment:

- to fetch PDU session to setup in E1 following logic as in e1_send_bearer_updates
- fill bearer context modification request with stored F1-U tunnel information
  during E1 reestablishment, otherwise it would initialized to 0 by default
- update GTP tunnel with the stored configuration after E1 reestablishment

- info coming from UE context setup/modification response messages in RRC

The following ASSERT is tirggered while testing 16 UE setup.

Assertion (NPRB>0 && (NPRB + RBstart <= BWPsize)) failed!
In PRBalloc_to_locationandbandwidth0() /home/ran/common/utils/nr/nr_common.c:286
Illegal NPRB/RBstart Configuration (1,48) for BWPsize 48

Corrected the get_start_stop_allocation calculation to fix the issue.
The implementation was wrong. The rbstop shall be the last rb that could
be allocated. Also the following two conditions are taken care

rbStart needs to be strictly smaller than rbStop

rbStart+rbSize needs to be smaller or equal to rbStop

The problem was that we confounded both conditions, so rbStart could
be equal to rbStop, which then leads to one PRB being allocated at the end.
Setting rbStop to BWPsize - 1 and making sure the above two conditions are
true does not make it lead to wrong allocations anymore.

textlog is, well, text log. The GUI part is totally useless.
Let's remove it.