feat(detector-gcp): collect hostname resource attribute from GCP Metadata API

[mwear]

Which problem is this PR solving?

This PR is mostly for convenience. When working on collecting host-id for non-cloud environments, I was looking at the AWS EC2 Detector and the GCP Detector. I noticed that the EC2 Detector collects both host.name and host.id, and the GCP Detector collects only host.id. I updated the GCP Detector to collect host.name for congruence with the EC2 Detector and also so that GCP users will not have to use the Host Detector, or worry about Detector ordering when collecing host.name and host.id.

Short description of the changes

• Collect host.name resource attribute in GCP Detector

[codecov]

Codecov Report

Merging #1364 (a4dd63d) into main (63e0fc9) will increase coverage by 0.01%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1364      +/-   ##
==========================================
+ Coverage   96.10%   96.11%   +0.01%     
==========================================
  Files          14       16       +2     
  Lines         898      952      +54     
  Branches      192      197       +5     
==========================================
+ Hits          863      915      +52     
- Misses         35       37       +2     

Impacted Files	Coverage Δ
...resource-detector-gcp/src/detectors/GcpDetector.ts	96.22% <100.00%> (ø)
...metry-resource-detector-gcp/src/detectors/index.ts	100.00% <0.00%> (ø)