feat: handle certificates:snis relation for Konnect

[czeslavo]

As Konnect does not support the API sugar that allows specifying SNIs on PUT /certificates, we should not fill them when an update of a certificate is performed.

It's still required for regular Kong Gateways as they would treat empty SNIs in a certificate as a signal to remove any existing SNIs associated with a certificate.

[codecov-commenter]

Codecov Report

Patch coverage: 0.79% and project coverage change: -0.27 ⚠️

Comparison is base (d19b622) 33.97% compared to head (03de312) 33.70%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #978      +/-   ##
==========================================
- Coverage   33.97%   33.70%   -0.27%     
==========================================
  Files         100      100              
  Lines       11906    12000      +94     
==========================================
  Hits         4045     4045              
- Misses       7468     7562      +94     
  Partials      393      393              

Impacted Files	Coverage Δ
cmd/common.go	4.29% <0.00%> (-0.81%)	⬇️
cmd/common_konnect.go	6.71% <0.00%> (ø)
cmd/convert.go	0.00% <0.00%> (ø)
cmd/diff.go	0.00% <0.00%> (ø)
cmd/reset.go	0.00% <0.00%> (ø)
cmd/root.go	0.92% <0.00%> (+<0.01%)	⬆️
cmd/sync.go	0.00% <0.00%> (ø)
cmd/validate.go	0.00% <0.00%> (ø)
cprint/color.go	82.85% <0.00%> (-7.77%)	⬇️
diff/diff.go	0.00% <0.00%> (ø)
... and 2 more

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.

[czeslavo]

@GGabriele Thanks for the actual fix! What would you say about such change? I think the only fix needed is to skip the "special" case that backfills SNIs in createUpdateCertificate method when we're running against Konnect.