In #31118, the format of bitcoind's `--help` output changed slightly in
a way that breaks `gen-bitcoin-conf.sh`, modify the script to accomodate
the new format, by starting after the line that says "Options:" and
strip the `-help` option and its description from the output.
This change:
1. Collects build artifacts in dedicated locations.
2. Allows running bitcoin-chainstate.exe with bitcoinkernel.dll directly
from the build tree on Windows.
the cmake build steps suggest a build/ directory, which breaks these
scripts. Additionally, in-tree builds are no longer allowed, so it makes
sense to update the code and the README accordingly.
this ensures bitcoind option help is the source of truth and also
gives an example conf file for users to customize and copy to their
data directory.
closes#10746
