Support for marshaling other types.

[bigkevmcd]

Changes

This adds support for marshaling bool values, and maps if they're used as the
values of expressions in a CEL overlay.

Submitter Checklist

These are the criteria that every PR should meet, please check them off as you
review them:

• Includes tests (if functionality changed/added)
• Includes docs (if user facing)
• Commit messages follow commit message best practices

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Release Notes

Marshaling of maps and boolean values in CEL expressions for the overlay mechanism should now work.

[tekton-robot]

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

File	Old Coverage	New Coverage	Delta
pkg/interceptors/cel/cel.go	87.9%	89.2%	1.3

[dibyom]

/kind feature
/approve
/lgtm

[tekton-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dibyom

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