fix(fn): use correct English plural for CRD name in schema fallback

[jonasz-lasut]

Description of your changes

requireSchemas() guessed the CRD's Kubernetes object name by naively appending "s" to the Kind (e.g. AccessEntry -> accessentrys) when falling back to required_resources on Crossplane/UXP versions that predate the required_schemas capability (< v2.2). Kinds with an irregular English plural (AccessEntry -> AccessEntries, Policy -> Policies, ...) never matched any real CRD, so the resource silently looked "unavailable" and schema resolution for it fell through to the built-in-types-only resolver, producing a misleading "schema not found" error even though the CRD existed and worked fine.

Use flect.Pluralize (already an indirect dependency, the same library Kubernetes codegen tooling uses) to compute the plural instead.

Fixes #116

I have:

• Read and followed Crossplane's contribution process.
• Added or updated unit tests for my change.

[jbw976]

nice, this looks to be a simple and straightforward way to fix the issue! I had looked into using https://pkg.go.dev/k8s.io/apimachinery/pkg/api/meta#UnsafeGuessKindToResource, but that looks to have some not very robust logic for handling words ending in y, which flect seems to handle more intelligently.

I've tested with /test-examples on a v2.1 control plane and everything is passing, so this doesn't seem to introduce obvious regressions either.

Thank you @jonasz-lasut!! 🙇‍♂️