Merge remote-tracking branch 'origin/cuup-load-tester' into integration_2025_w32 (!3547)

Add a CU-UP load tester and improve GTP performance

This adds a simple tester program for the CU-UP. It sets up a number of
UEs/bearers in the CU-UP via the E1 interface, then streams data in
downlink/uplink (as seen by the CU-UP). More information is available in
tests/nr-cuup/README.md.

Includes some fixes to properly verify that SCTP is installed, and use
"the right cmake way" to use it in cmake code (see commit for details).

doc/F1AP/F1-design.md

@@ -221,9 +221,7 @@ In the CU file:
   ignored, but we recommend to put `0.0.0.0` ("any")
 - Ports should match the ones in the DU config, but for simplicity and
   standards-conformity, simply set all to 2152:
-  - `local_s_portc` in CU should match `remote_n_portc` in DU
   - `local_s_portd` in CU should match `remote_n_portd` in DU
-  - `remote_s_portc` in CU should match `local_n_portc` in DU
   - `remote_s_portd` in CU should match `local_n_portd` in DU
 
 In the DU file:

doc/README.md

@@ -130,6 +130,8 @@ The other SDRs (AW2S, LimeSDR, ...) have no READMEs.
 # Testing
 
 - [UnitTests.md](./UnitTests.md) explains the unit testing setup
+- Component tests are under `tests/`. Currently, there is a simple CU-UP
+  tester, see the corresponding [README.md](../tests/nr-cuup/README.md).
 - [TESTBenches.md](./TESTBenches.md) lists the CI setup and links to pipelines
 
 # Developer tools