Replace flight navigation build id field with header (#88855)
Closes PACK-6536
- with deployment id available: a header contains the process.env.NEXT_DEPLOYMENT_ID , the client knows its dpl id already, so we can use that already
- with deployment id unavailable: a response field contains the BUILD_ID, keep the existing logic of storing the build id in the browser
It's unfortunate that we have to keep the BUILD_ID response field approach as a fallback, but oh well.
This has the benefit that we won't need the build id anymore when the deployment id is available.
If you use `output:export` and set `config.deploymentId` (i.e. enable skew protection) you are still expected to set these headers.
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- [x] Fallback behavior for when there is no deployment id
- [ ] Run deployment tests
