Handle CESQL parsing panics gracefully

[devguyio]

Proposed Changes

• 🐛 If parsing the CE SQL expression panics, treat it as an invalid expression.

Pre-review Checklist

• At least 80% unit test coverage
• E2E tests for any new behavior
• Docs PR for any user-facing impact
• Spec PR for any new API feature
• Conformance test for any change to the spec

Release Note

When the `new-trigger-filters` experimental feature is enabled, a bug was fixed where some invalid CE SQL expressions caused a crash eventing webhook. Now those expressions will be considered invalid and the webhook will continue functioning normally. 

[codecov]

Codecov Report

Merging #6140 (38b1eed) into main (6b9499f) will decrease coverage by 0.02%.
The diff coverage is 25.00%.

@@            Coverage Diff             @@
##             main    #6140      +/-   ##
==========================================
- Coverage   82.09%   82.06%   -0.03%     
==========================================
  Files         231      231              
  Lines        7765     7769       +4     
==========================================
+ Hits         6375     6376       +1     
- Misses        940      942       +2     
- Partials      450      451       +1     

Impacted Files	Coverage Δ
pkg/apis/eventing/v1/trigger_validation.go	84.66% <25.00%> (-1.64%)	⬇️

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[knative-metrics-robot]

The following is the coverage report on the affected files.
Say /test pull-knative-eventing-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/apis/eventing/v1/trigger_validation.go	94.3%	92.7%	-1.6

[matzew]

/lgtm
/approve

[knative-prow-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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• OWNERS [devguyio,matzew]

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