[WIP]: feat: triggerv2 supports cross namespace references

[Cali0707]

E2E tests will be added once knative/eventing#8157 merges

Fixes #4080

TODO:

• Channel
• E2E tests (broker-based from core)
• Unit tests

Proposed Changes

Release Note

Docs

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Cali0707

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[Cali0707]

/cc @Leo6Leo @creydr

[codecov]

Codecov Report

Attention: Patch coverage is 38.88889% with 11 lines in your changes missing coverage. Please review.

Project coverage is 48.45%. Comparing base (073bcd2) to head (a1bb7a8).
Report is 49 commits behind head on main.

Files with missing lines	Patch %	Lines
...ol-plane/pkg/reconciler/trigger/v2/controllerv2.go	22.22%	7 Missing ⚠️
...ntrol-plane/pkg/reconciler/trigger/v2/triggerv2.go	55.55%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4060      +/-   ##
==========================================
+ Coverage   48.41%   48.45%   +0.03%     
==========================================
  Files         244      244              
  Lines       14514    14554      +40     
==========================================
+ Hits         7027     7052      +25     
- Misses       6777     6790      +13     
- Partials      710      712       +2     

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[Cali0707]

/assign @pierDipi

[pierDipi]

/retest

[Cali0707]

/test upgrade-tests
/cc @pierDipi any feedback?