Add more cel extensions

[venc0r]

Feature request

the docs say the cel interceptor should support all extensions

All the functionality from the cel-go project’s CEL extension is available in your CEL expressions.

Over the last months there are new extensions added to cel, but not enabled in the cel-eval interceptor.

Use case

I want to get a slice of an array like: [1,2,3,4].slice(1,3) => [2,3]

[khrm]

@venc0r Won't a update to the latest library fix this? #1718

[khrm]

/assign @khrm

[khrm]

/assign @bigkevmcd

[khrm]

It will be fixed by #1730

[bigkevmcd]

@venc0r #1730 will add most of the new CEL extensions, I deliberately didn't add the Proto extension as I'm unsure of a use case for it, but the slices, sets and math extensions are now in there.