Add unit tests and fuzz tests for get_key_pair_info

[Xiaohanjlll]

libspdm_req_get_key_pair_info.c
- Fuzz testing coverage : 90.1%
- 
- run time : 1 days, 00 hrs, 00 min, 00 sec
- 
- overall results :
-   cycles done :   374  
-   corpus count :  53   
-   saved crashes : 0 
-   saved hangs :   0 

libspdm_rsp_key_pair_info.c
- Fuzz testing coverage : 77.6 %
- 
- run time : 1 days, 00 hrs, 00 min, 00 sec
- 
- overall results :
-   cycles done :   1742  
-   corpus count :  21   
-   saved crashes : 0 
-   saved hangs :   0 

[Wenxing-hou]

I am reviewing the PR. Thanks.

[steven-bellock]

@jyao1 feel free to merge as you see fit.