Allow multiple CA Certificates

[aledbf]

What this PR does / why we need it:

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #4234

Special notes for your reviewer:

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aledbf

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[aledbf]

/retest

[aledbf]

/retest

[aledbf]

/retest

[codecov-io]

Codecov Report

Merging #4556 into master will increase coverage by 0.02%.
The diff coverage is 59.25%.

@@            Coverage Diff             @@
##           master    #4556      +/-   ##
==========================================
+ Coverage   59.34%   59.37%   +0.02%     
==========================================
  Files          89       89              
  Lines        6823     6823              
==========================================
+ Hits         4049     4051       +2     
+ Misses       2338     2337       -1     
+ Partials      436      435       -1

Impacted Files	Coverage Δ
internal/ingress/sslcert.go	0% <ø> (ø)	⬆️
internal/ingress/controller/store/backend_ssl.go	43.29% <0%> (-3.58%)	⬇️
internal/net/ssl/ssl.go	52.76% <69.56%> (+1.66%)	⬆️
internal/watch/file_watcher.go	84.61% <0%> (+3.84%)	⬆️

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