cmake: Set top-level target output locations

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.

contrib/devtools/gen-bitcoin-conf.sh

@@ -6,7 +6,7 @@
 export LC_ALL=C
 TOPDIR=${TOPDIR:-$(git rev-parse --show-toplevel)}
 BUILDDIR=${BUILDDIR:-$TOPDIR/build}
-BINDIR=${BINDIR:-$BUILDDIR/src}
+BINDIR=${BINDIR:-$BUILDDIR/bin}
 BITCOIND=${BITCOIND:-$BINDIR/bitcoind}
 SHARE_EXAMPLES_DIR=${SHARE_EXAMPLES_DIR:-$TOPDIR/share/examples}
 EXAMPLE_CONF_FILE=${EXAMPLE_CONF_FILE:-$SHARE_EXAMPLES_DIR/bitcoin.conf}