Changes:
- Name local testnet output folders same as the `make` taget.
- Move both `Jenkinsfile`s to `ci` folder to avoid cluttering repo root.
- Separate builds by platform so logs from macos and linux hosts don't get mixed.
- Detect platform and architecture from Jenkins Job path to use one Jenkinsfile.
- Divide shell commands into as many stages as possible to make debugging easier.
- Generalize running testnets via a `launchLocalTestnet()` Groovy method.
- Handle uploading of results of running testnets stage-by-stage basis.
- Use `catchError()` to upload test results while marking job as failed.
- Abort previously started PR build jobs usin `disableConcurrentBuilds()`.
- Throttle jobs using the new `throttleJobProperty()` function.
Builds:
- https://ci.status.im/job/nimbus/job/nimbus-eth2/job/platforms/job/linux/job/x86_64/
- https://ci.status.im/job/nimbus/job/nimbus-eth2/job/platforms/job/macos/job/x86_64/
- https://ci.status.im/job/nimbus/job/nimbus-eth2/job/platforms/job/macos/job/aarch64/
Signed-off-by: Jakub Sokołowski <jakub@status.im>
