[ty] Update mypy_primer, add egglog-python project (#20078)
Now that https://github.com/astral-sh/ruff/pull/20263 is merged, we can
update mypy_primer and add the new `egglog-python` project to
`good.txt`. The ecosystem-analyzer run shows that we now add 1,356
diagnostics (where we had over 5,000 previously, due to the unsupported
project layout).
