Add `InstanceOffer.backend_data` + reserved GCP A4 #5676

Job	Run time
compute-version	4s
build-docs / build-docs	1m 52s
build-artifacts / frontend-build	7s
build-artifacts / code-lint	51s
build-artifacts / runner-test (ubuntu-latest)	57s
build-artifacts / runner-test (macos-latest)	1m 9s
build-artifacts / gateway-build	10s
build-artifacts / python-build	24s
build-artifacts / python-test (macos-latest, 3.10)	3m 15s
build-artifacts / python-test (macos-latest, 3.11)	2m 42s
build-artifacts / python-test (macos-latest, 3.9)	2m 15s
build-artifacts / python-test (windows-latest, 3.10)	1m 51s
build-artifacts / python-test (ubuntu-latest, 3.13)	3m 51s
build-artifacts / python-test (ubuntu-latest, 3.11)	3m 53s
build-artifacts / python-test (macos-latest, 3.12)	3m 36s
build-artifacts / python-test (ubuntu-latest, 3.12)	4m 2s
build-artifacts / python-test (ubuntu-latest, 3.10)	4m 5s
build-artifacts / python-test (macos-latest, 3.13)	3m 0s
build-artifacts / python-test (windows-latest, 3.11)	2m 12s
build-artifacts / generate-json-schema	16s
build-artifacts / python-test (windows-latest, 3.12)	1m 50s
build-artifacts / python-test (ubuntu-latest, 3.9)	4m 13s
build-artifacts / python-test (windows-latest, 3.9)	1m 50s
build-artifacts / python-test (windows-latest, 3.13)	2m 7s
build-artifacts / runner-compile (ubuntu-24.04, linux, amd64)	46s
build-artifacts / runner-compile (ubuntu-24.04-arm, linux, arm64)	31s
upload-pre-pypi-artifacts / upload-pre-pypi-artifacts	15s
upload-post-pypi-artifacts / upload-post-pypi-artifacts	18s
	52m 22s

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