Start the merging-rebase to v2.40.1

I previously merged the `main` branch into the (deviating)
v2.40.1.windows.1, in the hopes to make future rebases easier. But that
is not the case, unfortunately.

So let's do a merging-rebase to v2.40.1 (which is already integrated
into Git for Windows' `main` branch), to allow for reordering commits
and cleaning up the branch thicket.

This also allows me to fix my mistake where I should have made the "Drop
the old-style runtime-prefix handling in `interpolate_path()`" commit a
fixup! to the commit that needed to be dropped.

This commit starts the rebase of 1c95112 to 2df31ab

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho