hadrian: Drop --configure support

Hadrian's `--configure` support has long been a point of contention.
While it's convenient, it also introduces a fair bit of implementation
complexity and quite a few non-trivial failure modes
(see #19804, 17883, and #15948). Moreover, the feature is actively
misleading to the user: `./configure` is the primary means for the user
to inform the build system about the system environment and in general
will require input from the user.

This commits removes the feature, replacing the flag with a stub
message informing the user of the deprecation.

Closes #20167.