feat(ci): add a special label to run full test matrix

[slonka]

This PR gives the contributor an ability to run the whole matrix test suite by adding "ci/run-full-matrix" label to the PR.

The master branch is broken now because of #4769 but you can see from the history that all targets were triggered.

Signed-off-by: slonka slonka@users.noreply.github.com

Checklist prior to review

• Link to docs PR or issue -- CI improvement
• Link to UI issue or PR -- not a UI issue
• Is the issue worked on linked? -- not reported as a bug
• Unit Tests -- not a kuma feature
• E2E Tests -- not a kuma feature
• Manual Universal Tests -- not a kuma feature, but tested manually on circleCI
• Manual Kubernetes Tests -- not a kuma feature
• Do you need to update UPGRADE.md? -- no
• Does it need to be backported according to the backporting policy? -- no

[codecov-commenter]

Codecov Report

Merging #4770 (6f38d53) into master (c4809e1) will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4770      +/-   ##
==========================================
+ Coverage   46.35%   46.36%   +0.01%     
==========================================
  Files         690      690              
  Lines       46942    46942              
==========================================
+ Hits        21762    21767       +5     
+ Misses      23254    23251       -3     
+ Partials     1926     1924       -2     

Impacted Files	Coverage Δ
pkg/plugins/runtime/gateway/route/sorter.go	71.79% <0.00%> (+5.12%)	⬆️
pkg/plugins/leader/postgres/leader_elector.go	89.36% <0.00%> (+6.38%)	⬆️

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[jakubdyszkiewicz]

awesome!