Adding support for `customTypes` in CEL environment

[AshwinSriram11]

Feature Description

Problem Statement:
Currently, resources are declared with cel.AnyType in kro due to which it lacks compile-time safety. This makes it hard to find errors early. Enabling customTypes would help set up validation and reduce failures. Currently, CEL expressions rely on emulation mechanics for validation. Implementing customTypes would allow CEL to validate expressions rather than depending on emulation natively. The emulation logic is in pkg/graph/emulator

Proposed Solution:

Alternatives Considered:

Additional Context:

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[a-hilaly]

This is fixed in #756