[bazel,openocd] Consider switching to the github mirror instead of sourceforge

Nobody has claimed this yet.

### Description

Sourceforge is not the most reliable platform and the last outage killed our CI for 24h. Since we already rely heavily on github, it would make sense to use [the github official mirror](https://github.com/openocd-org/openocd) instead of sourceforge. This is not trivial though: even though the releases are not on github as well, they are not the same as on github. Specifically:
- the sourceforge release contain the `jimtcl` code and possibly other code included by submodule,
- the github release does not contain this code, *nor* the submodule, essentially making them unusable because the bootstrap script will fail,
- having to run git submodule to boostrap also means that we would have to depend on possibly other sources and is not ideal for airgapped builds?

Possibilities:
- Fork openocd and have our own release action that create an already bootstrapped source code.
- Ask OpenOCD devs to release the same source on sourceforge and github
- (More general) Maintain a download cache in the CI to avoid redownloading things all the time

Start by locating the Bazel dependency and bootstrap script that download OpenOCD, then compare the SourceForge and GitHub release archives described in the issue. Determine how submodules and jimtcl affect CI and air-gapped builds, and define whether a mirrored release, an OpenOCD fork, or a download cache is the intended outcome.

Written by the indexing model from the issue text.