Add check that there aren't projects with similar names

[fingolfin]

At some point the same project was imported by two people independently, once as laz_perf and once as LAZperf. That's unfortunate.

Perhaps we could add an automated check to prevent having projects which differ only by case (and underscores). The package registry also has such checks, but it would be better to catch that sooner, i.e. here, not only after we hit the registry.

See PR #3554 for an older attempt to do this (but that was made before the switch to Buildkite, so is using Azure Pipelines, but perhaps parts can be salvaged or can serve as inspiration).

Of course the code of the relevant checks in the registry might also be an inspiration (in fact it seems preferable to use the exact same check)