The Microsoft-hosted Azure agents are 2-core; the GitHub-hosted runners
are 4-core (3-core on macOS arm64). Measured on an identical `koch boot
-d:release` against our own Docs CI, the GitHub runners are ~2.3x
faster:
Linux boot 8.2 min -> 4.5 min
Windows boot 11.4 min -> 4.9 min
macOS boot 4.2 min -> 1.7 min
csources 2.0 min -> 0.8 min
`.github/workflows/ci_main.yml` keeps the same six jobs, the same runner
images, the same dependency installation and the same `ci/funs.sh` entry
points, so this is a move, not a redesign.
Differences forced by the platform:
* `[skip ci]` is handled natively by GitHub, so the `nimIsCiSkip` step
and the `skipci` variable that gated every step are gone. `nimIsCiSkip`
stays in `ci/funs.sh` for the version branches.
* `SYSTEM_ACCESSTOKEN` is gone: `testament/azure.nim` activates on
`TF_BUILD`, which is unset here, so it no-ops. This also removes a flake
source, where a failure to create the Azure test run cancelled an
otherwise green job.
* `concurrency: cancel-in-progress` replaces Azure's `pr.autoCancel`.
* `NIM_TESTAMENT_BATCH` defaults to `_` explicitly: a matrix-derived env
var is set to the empty string rather than left unset, so `getEnv`'s
default would not have applied.
`disabled: "azure"` was the only way to skip a test on the main
pipeline, so add `disabled: "github"` (`isGithubActions`) to replace it;
`azure` is kept as deprecated, alongside `travis` and `appveyor`.
Two manual steps remain: disabling the Azure pipeline definition, and
pointing the required status checks at the new job names.
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Co-authored-by: ringabout <43030857+ringabout@users.noreply.github.com>
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