Support force cache even when server doesn't set the Date header #8860

Job	Run time
Generate Code	1m 30s
Rego PR checks	2m 15s
Go Lint	2m 35s
Check Generated	30s
Go Build (linux amd64)	3m 33s
Go Build (linux arm64)	3m 3s
Go Build (windows)	3m 13s
Go Build (darwin)	3m 25s
Go compat build/test (ubuntu-22.04, 1.19)	4m 25s
Go compat build/test (macos-latest, 1.19)	4m 21s
Go Test (linux)	4m 24s
Go Test (darwin)	4m 20s
Go Race Detector	4m 24s
WASM	12s
docker image smoke test	37s
smoke-test-binaries (ubuntu-22.04, opa_linux_amd64)	16s
smoke-test-binaries (ubuntu-22.04, opa_linux_amd64_static, disabled)	22s
smoke-test-binaries (macos-latest, opa_darwin_amd64)	26s
smoke-test-binaries (windows-latest, opa_windows_amd64.exe)	29s
	44m 20s

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