Fix update loop in backup selection resource and add an example

[turkenf]

Description of your changes

This PR adds a custom diff func for fields that cause loops in the selection resource and adds an example.

2025-05-27T22:25:00+03:00	DEBUG	provider-aws	Diff detected	{"uid": "4c7480f8-10f0-47ee-800e-713dc148a8e5", "name": "example-selection", "gvk": "backup.aws.upbound.io/v1beta1, Kind=Selection", "instanceDiff": "*terraform.InstanceDiff{mu:sync.Mutex{state:0, sema:0x0}, Attributes:map[string]*terraform.ResourceAttrDiff{\"condition.0.string_equals.#\":*terraform.ResourceAttrDiff{Old:\"0\", New:\"0\", NewComputed:false, NewRemoved:false, NewExtra:interface {}(nil), RequiresNew:false, Sensitive:false, Type:0x0}, \"condition.0.string_like.#\":*terraform.ResourceAttrDiff{Old:\"0\", New:\"0\", NewComputed:false, NewRemoved:false, NewExtra:interface {}(nil), RequiresNew:false, Sensitive:false, Type:0x0}, \"condition.0.string_not_equals.#\":*terraform.ResourceAttrDiff{Old:\"0\", New:\"0\", NewComputed:false, NewRemoved:false, NewExtra:interface {}(nil), RequiresNew:false, Sensitive:false, Type:0x0}, \"condition.0.string_not_like.#\":*terraform.ResourceAttrDiff{Old:\"0\", New:\"0\", NewComputed:false, NewRemoved:false, NewExtra:interface {}(nil), RequiresNew:false, Sensitive:false, Type:0x0}, \"condition.101782678.string_equals.#\":*terraform.ResourceAttrDiff{Old:\"0\", New:\"0\", NewComputed:false, NewRemoved:false, NewExtra:interface {}(nil), RequiresNew:false, Sensitive:false, Type:0x0}, \"condition.101782678.string_like.#\":*terraform.ResourceAttrDiff{Old:\"0\", New:\"0\", NewComputed:false, NewRemoved:false, NewExtra:interface {}(nil), RequiresNew:false, Sensitive:false, Type:0x0}, \"condition.101782678.string_not_equals.#\":*terraform.ResourceAttrDiff{Old:\"0\", New:\"0\", NewComputed:false, NewRemoved:false, NewExtra:interface {}(nil), RequiresNew:false, Sensitive:false, Type:0x0}, \"condition.101782678.string_not_like.#\":*terraform.ResourceAttrDiff{Old:\"0\", New:\"0\", NewComputed:false, NewRemoved:false, NewExtra:interface {}(nil), RequiresNew:false, Sensitive:false, Type:0x0}}, Destroy:false, DestroyDeposed:false, DestroyTainted:false, RawConfig:cty.NilVal, RawState:cty.NilVal, RawPlan:cty.NilVal, Meta:map[string]interface {}(nil)}"}

I have:

• Read and followed Crossplane's contribution process.
• Run make generate and committed the results (ideally in a separate commit).
• Not made any manual changes to generated files, and verified this with make check-diff.

How has this code been tested

Uptest-examples/backup/v1beta1/selection.yaml

[turkenf]

/test-examples="examples/backup/v1beta1/selection.yaml"

[sergenyalcin]

Thanks @turkenf LGTM!