[processor/resourcedetection] Add back host.name on GKE

[mx-psi]

Description:

Adds back the host.name attribute (coming from instance/hostname) when running on GKE.

This metadata endpoint is available on GKE nodes of any type, and it was possible to have this attribute on GKE before #10347

Link to tracking Issue: Fixes #12354

[dashpole]

See #10486 (comment). It unfortunately isn't available on GKE when using workload identity.

[mx-psi]

See #10486 (comment). It unfortunately isn't available on GKE when using workload identity.

@dashpole Thanks for the link. Is it possible to identify when workload identity is being used? (Will investigate this, but maybe you know the answer right away :))

[dashpole]

It isn't really possible for the collector to know. The GCE metadata endpoints just won't be available in that case.

[mx-psi]

I added a addFallible method to the builder, so that the error is only logged when GCEHostname fails and does not make the whole processor fail. Is this solution acceptable to you @dashpole?

I understand that this can be also gathered through the downward API, but our biggest issue with users is currently misconfigurations and this makes it a lot easier (and restores the behavior that existed before when not using workload identity and was removed without prior warning).