fix(cli): send JSON struct for enterprise portal status update

[kriscoleman]

Shortcut Story

sc-136041

Summary

Fixes the replicated enterprise-portal status update command so that it sends a proper JSON object ({\"status\":\"...\"}) instead of a bare JSON string, which was causing the API to return a 400 error.

Also updates the CLI help text to enumerate the valid statuses (active, inactive, pending) instead of the vague "any other valid status" wording.

Changes

• Updated UpdateEnterprisePortalStatus in pkg/kotsclient/enterprise-portal.go to construct and send an UpdateEnterprisePortalStatusRequest struct.
• Added UpdateEnterprisePortalStatusRequest struct with a status JSON field.
• Added pkg/kotsclient/enterprise-portal_test.go with unit tests covering all enterprise portal client methods.
• Updated --help text and --status flag description in cli/cmd/enterpriseportal_status_update.go to list valid statuses.

UAT

1. Run the new unit tests: go test ./pkg/kotsclient/... -run TestEnterprisePortalClient -v
2. Verify the CLI builds: go build ./cli/...
3. Verify the updated help text: go run ./cli enterprise-portal status update --help
4. (Optional) Run replicated enterprise-portal status update --status inactive against a valid app and confirm it succeeds without a 400 error.

[kriscoleman]

Question: why doesn't the enterprise-portal command show under replicated help?