Change ISM_GAIN PI data to cover -Inf, -24 to +12 dB. Include -128...
Reason why this change is needed
- It was decided that ISM gain should cover range -24 to +12 dB.
Description of the change
- Updated range for ISM_GAIN PI data to be -Inf, -24 dB to +12 dB
- Added -Inf test cases to pytest for gain and directivity PI data
Related to #1154