## Issue Addressed
Closes https://github.com/sigp/lighthouse/issues/3656
## Proposed Changes
* Replace `set-output` by `$GITHUB_OUTPUT` usage
* Avoid rate-limits when installing `protoc` by making authenticated requests (continuation of https://github.com/sigp/lighthouse/pull/3621)
* Upgrade all Ubuntu 18.04 usage to 22.04 (18.04 is end of life)
* Upgrade macOS-latest to explicit macOS-12 to silence warning
* Use `actions/checkout@v3` and `actions/cache@v3` to avoid deprecated NodeJS v12
## Additional Info
Can't silence the NodeJS warnings entirely due to https://github.com/sigp/lighthouse/issues/3705. Can fix that in future.
## Issue Addressed
The release CI is currently broken due to the addition of the `protoc` dependency. Here's a failure of the release flow running on my fork: https://github.com/michaelsproul/lighthouse/actions/runs/3155541478/jobs/5134317334
## Proposed Changes
- Install `protoc` on Windows and Mac so that it's available for `cargo install`.
- Install an x86_64 binary in the Cross image for the aarch64 platform: we need a binary that runs on the host, _not_ on the target.
- Fix `macos` local testnet CI by using the Github API key to dodge rate limiting (this issue: https://github.com/actions/runner-images/issues/602).
## Issue Addressed
https://github.com/sigp/lighthouse/issues/3091
Extends https://github.com/sigp/lighthouse/pull/3062, adding pre-bellatrix block support on blinded endpoints and allowing the normal proposal flow (local payload construction) on blinded endpoints. This resulted in better fallback logic because the VC will not have to switch endpoints on failure in the BN <> Builder API, the BN can just fallback immediately and without repeating block processing that it shouldn't need to. We can also keep VC fallback from the VC<>BN API's blinded endpoint to full endpoint.
## Proposed Changes
- Pre-bellatrix blocks on blinded endpoints
- Add a new `PayloadCache` to the execution layer
- Better fallback-from-builder logic
## Todos
- [x] Remove VC transition logic
- [x] Add logic to only enable builder flow after Merge transition finalization
- [x] Tests
- [x] Fix metrics
- [x] Rustdocs
Co-authored-by: Mac L <mjladson@pm.me>
Co-authored-by: realbigsean <sean@sigmaprime.io>
## Issue Addressed
N/A
## Proposed Changes
Since Rust 1.62, we can use `#[derive(Default)]` on enums. ✨https://blog.rust-lang.org/2022/06/30/Rust-1.62.0.html#default-enum-variants
There are no changes to functionality in this PR, just replaced the `Default` trait implementation with `#[derive(Default)]`.
## Issue Addressed
Resolves https://github.com/sigp/lighthouse/issues/2763
## Proposed Changes
- Add a workflow which tests that local testnet starts successfully
- Added `set` option into the scripts in order to fail fast so that we can notice errors during starting local testnet.
- Fix errors on MacOS
- The redirect `&>>` is supported since bash v4 but the version bundled in macOS(11.6.1) is v3. a54f119c9b
