runtime: revert recent Windows crashdump changes

Recent changes to runtime enabled crashdumps, which under some
circumstances apparently might result in memory being uploaded to
Microsoft. A change like this should go through the proper proposals
process where we can discuss how to gate it and what all of its
implications are.

This reverts CL 307372 and its cleanup CL 360617.

Change-Id: If2e74015899d746831da40546c82eacacdf739e1
Reviewed-on: https://go-review.googlesource.com/c/go/+/362454


Trust: Jason A. Donenfeld <Jason@zx2c4.com>
Run-TryBot: Jason A. Donenfeld <Jason@zx2c4.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>