The structure in which was snr will be a "SRS job" in a follow-up
commit, so the snr parameter cannot be stored in there (and it is also
not necessary to do so, as it can be local to the function handling
nr_srs_rx_procedures()).

Correctly read SRS SNR through FAPI message in nr_ulsim. Switch to SRS
BEAMMANAGEMENT as only this message returns the actual SNR (unlike
CODEBOOK). Add asserts to check what is returned is valid data in the
sense of the test.
Signed-off-by: Robert Schmidt <robert.schmidt@openairinterface.org>