Refactor submit config resolution by platform

[sjchmiela]

Summary

• Remove the platform input from eas/resolve_submit_config and infer it from the build ID
• Split submit config resolution into Android and iOS modules for easier review
• Resolve Android service account JSON directly from GraphQL and use UserError/SystemError for failures
• Rename the config output to config_json

Testing

• yarn workspace @expo/build-tools typecheck
• yarn exec oxfmt --check packages/build-tools/src/steps/functions/resolveSubmitConfig/index.ts packages/build-tools/src/steps/functions/resolveSubmitConfig/common.ts packages/build-tools/src/steps/functions/resolveSubmitConfig/android.ts packages/build-tools/src/steps/functions/resolveSubmitConfig/ios.ts packages/build-tools/src/steps/easFunctions.ts packages/build-tools/package.json

[github-actions]

❌ It looks like a changelog entry is missing for this PR. Add it manually to CHANGELOG.md.
⏩ If this PR doesn't require a changelog entry, such as if it's an internal change that doesn't affect the user experience, you can add the "no changelog" label to the PR.