fix: remove ingress option from delivery format

[Cali0707]

Removes the delivery format option we had before, and aligns the code with the approach used for other similar fields in the delivery spec.

Proposed Changes

• remove the ingress option from the format type
• create a type alias and some constants for the format type options

[Cali0707]

/cc @matzew

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.85%. Comparing base (9eed163) to head (42d46a5).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8086      +/-   ##
==========================================
- Coverage   67.85%   67.85%   -0.01%     
==========================================
  Files         367      367              
  Lines       17356    17354       -2     
==========================================
- Hits        11777    11775       -2     
  Misses       4844     4844              
  Partials      735      735              

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[matzew]

why not calling it structured?

[Cali0707]

This was an idea from #8080 (comment), I'm personally happy either way :)

[matzew]

ok, I was guess it was along those lines.

OK.

[matzew]

/lgtm
/approve

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Cali0707, matzew

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