CI: Add channel emulation in one test

• Add channel emulation in test "5G CU/DU RFsim" by enabling AWGN with some noise and path loss (values to be discussed)
• Enable high MCS in that same test
• Place documentation link for channel simu documentation in main doc README.md

Detailed changes:

1. Channel Simulation: We're now using OAI channel simulation in the CI to introduce impairments to the channel. This allows us to simulate various network conditions and observe their effects on the system.
2. New telnet module ciUE: this module implements nrUE specific Telnet functions for the CI
3. Test Scenarios: We've added new test scenarios that cover different sync loss scenarios. These tests help us ensure that the OAI UE can handle these conditions and recover from them if necessary.

• Updated container_5g_f1_rfsim.xml to include new test cases