Use new expr-lang builtins instead of pkg functions

[crenshaw-dev]

Describe the solution you'd like

expr-lang has included int, float, and string functions since 1.14.0. Argo Workflows currently uses expr 1.16.9. Instead of using those functions as implemented in argoproj/pkg, we should use the built-ins.

We should also inline the implementation of jsonpath, since it is trivial and doesn't make sense to externalize to the pkg repo.

This simplifies maintenance, because we don't have to worry about the pkg repo lifecycle as much.

Additional context

More info here: argoproj/argo-cd#22175

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