add command to debug loading from keystore

[nickysemenza]

❯ ./gokeyless --keystore-debug -c ~/Desktop/nicky.yaml
2023/05/17 11:04:38 [INFO] loading pkcs11:token=SoftHSM2%20Token;id=%03?module-path=/opt/homebrew/opt/softhsm/lib/softhsm/libsofthsm2.so&pin-value=1234...
2023/05/17 11:04:38 [DEBUG] add signer with SKI: 406550d87609ecae021a83ef2c1f372c08f42699 (https://crt.sh/?ski=406550d87609ecae021a83ef2c1f372c08f42699)

Through this, reproduction of #324 is possible in tests, without the need to setup PKI.

[codecov-commenter]

Codecov Report

Merging #351 (cf568bc) into master (e43c6e9) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #351   +/-   ##
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  Coverage   51.92%   51.92%           
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  Files          22       22           
  Lines        2708     2708           
=======================================
  Hits         1406     1406           
  Misses       1153     1153           
  Partials      149      149