Create an ARM64 GitHub Actions Runner that repositories can use to build / test on ARM64

[trask]

Opening as a public tracking issue, it looks like I have access to create it.

[trask]

[trask]

we can also create a Windows ARM64 runner if needed

I set max concurrency to 20, but we can update that if needed

[lalitb]

@trask Is this the correct runner - otel-linux-arm64, as it doesn't seem to be available - https://github.com/open-telemetry/opentelemetry-rust/actions/runs/9522286107/job/26251528030?pr=1884

[trask]

it looks like we have to give permission to the runner for each repository, I've given permission to opentelemetry-rust and opentelemetry-rust-contrib now

[trask]

I've also given permission to opentelemetry-cpp (#2151)

[trask]

I've updated the runner to 4-cores to match the default linux runners (https://docs.github.com/en/actions/using-github-hosted-runners/about-github-hosted-runners/about-github-hosted-runners#standard-github-hosted-runners-for-public-repositories)

[trask]

I also created otel-linux-arm64-8-cores for comparison testing

[trask]

I also gave permission to the ARM64 runners to the opentelemetry-demo repository (cc @austinlparker)

[dmathieu]

Note that some SIGs are using actuated to do this (not on windows). https://github.com/open-telemetry/community/blob/main/docs/using-actuated.md