This adds handwritten list-resource support for google_compute_instance.

Changes in this PR:

• add resource identity support to google_compute_instance (project, zone, name identity fields, wired into read and import)
• add handwritten google_compute_instance list resource (list_google_compute_instance.go)
• register the Compute Instance list resource in the framework provider
• add acceptance coverage for terraform query identity results
• add acceptance coverage for plannable import via ImportBlockWithResourceIdentity
• add list-resource documentation for google_compute_instance

Testing

make testacc TEST=./google/services/compute TESTARGS='-run=TestAccComputeInstanceListResource_queryIdentity$$'

=== RUN   TestAccComputeInstanceListResource_queryIdentity
--- PASS: TestAccComputeInstanceListResource_queryIdentity (45.23s)
PASS
ok  	github.com/hashicorp/terraform-provider-google/google/services/compute	46.312s

make testacc TEST=./google/services/compute TESTARGS='-run=TestAccComputeInstance_importBlockWithResourceIdentity$$'

=== RUN   TestAccComputeInstance_importBlockWithResourceIdentity
--- PASS: TestAccComputeInstance_importBlockWithResourceIdentity (66.07s)
PASS
ok  	github.com/hashicorp/terraform-provider-google/google/services/compute	67.183s

Release Note Template for Downstream PRs (will be copied)

See Write release notes for guidance.

compute: add list-resource support for `google_compute_instance`

compute: add resource-identity support to `google_compute_instance`