Improve external-name config of iot thing type

[mbbush]

Description of your changes

The aws iot ThingType resource uses a parameter called "name" as its terraform id. Unfortunately, when it was first implemented, it was done using IdentifierFromProvider, which means that creating a new managed resource always attempts to create a new external resource, even if there already is one with the same name. For this particular resource, this results in errors from the AWS api.

The best external name config would be config.NameAsIdentifier, which would remove the redundant name property from both spec.forProvider and spec.initProvider, and initialize the name from metadata.name. But that's a breaking api change.

The next best external name config would be config.TemplatedStringAsIdentifier("", "{{ .parameters.name }}"), but that will (correctly) set name as an identifier field, which will remove it from spec.initProvider, which is also a breaking change.

So this is the best I can do at the moment without changing the schema. The content of the external name remains the same, but now crossplane knows how to construct it from the spec, so it can check for resource existence before trying to create it.

Because name is part of the id, but not set as an identifier field, various edge cases where the user omits it may continue to fail in less-than-ideal ways, but that's not a change from current behavior.

Fixes #

I have:

• Read and followed Crossplane's contribution process.
• Run make reviewable to ensure this PR is ready for review.
• Added backport release-x.y labels to auto-backport this PR if necessary.

How has this code been tested

Running uptest on the pr.

Manually confirming that the external name is the in the same format both before and after this change.

[mbbush]

/test-examples="examples/iot/v1beta1/thingtype.yaml"

[mbbush]

/test-examples="examples/iot/v1beta2/thingtype.yaml"

[mbbush]

/test-examples="examples/iot/v1beta1/thingtype.yaml,examples/iot/v1beta2/thingtype.yaml"

[turkenf]

/test-examples="examples/iot/v1beta2/thingtype.yaml"

[turkenf]

/test-examples="examples/iot/v1beta1/thingtype.yaml"

[turkenf]

Thank you @mbbush, LGTM.