fix(cd): send correct DTO envelope for service/environment/infrastructure -f uploads/create

[BlueLabelscotch]

Problem

harness create/update service|environment|infrastructure -f <file>.yaml failed with:
API error 400: identifier: cannot be empty

The Harness servicesV2, environmentsV2, and infrastructures APIs don't accept
the plain resource YAML you'd export from Harness Studio (e.g. a bare service:
block). They require a DTO envelope instead: identity fields
(identifier, name, orgIdentifier, projectIdentifier, ...) at the top level,
plus the full resource YAML embedded as a string under a yaml key. The CLI's
-f file-body path was JSON-encoding the raw YAML and sending it as-is, so the API
saw no top-level identifier and rejected it.
Separately, create/update connector (and other nouns using
create_body_wrap/update_body_wrap, e.g. organization/project/secret) had a
latent double-wrap bug: if -f was given a file already wrapped in its top-level
key (e.g. a Studio export shaped as {"connector": {...}}), the CLI would wrap it
again into {"connector": {"connector": {...}}}.

Fix

• Added a new spec option, file_body_yaml_envelope: <key>, and a buildYamlEnvelope
  helper in pkg/registry/endpoint.go that builds the API's required envelope from
  the -f file, handling all three shapes seen in real sample files: already an
  envelope (has yaml:), wrapped (e.g. service: block), or flat (no wrapper).
• Wired file_body_yaml_envelope onto the six create/update endpoints for
  service, environment, and infrastructure in pkg/spec/cd.spec.yaml.
• Added an unwrapIfAlreadyWrapped guard to the generic create_body_wrap/
  update_body_wrap file-body path so it detects an already-wrapped -f file and
  avoids double-wrapping (fixes the connector edge case and any other noun sharing
  this code path).

Testing

Verified live against a real Harness account:

• harness update service <id> -f service.yml — previously 400, now succeeds.
• harness update environment <id> -f environment.yml (flat shape) — succeeds.
• harness update infrastructure <id> -f infrastructure-definition.yml (already
  envelope shape) — succeeds.
• harness update connector <id> --set description=... — sanity-checked unaffected.