enabling kernel dump options in GENERIC

[Mark Johnston]

Hi,

Over the past couple of years, a number of kernel dump features have
been added: encryption, compression and dumping to a remote host
(netdump). These features are currently all omitted from GENERIC.

Adding the EKCD, GZIO, ZSTDIO and NETDUMP kernel options gives only a
small increase in the size of amd64 GENERIC kernels:

stock GENERIC: 31026016 bytes
modified GENERIC: 31033000 bytes

stock GENERIC-NODEBUG: 30995592 bytes
modified GENERIC-NODEBUG: 31002680 bytes

(The GZIO and ZSTDIO options also enable support for compressed user core
dumps.) Therefore, I'd like to propose enabling these features by default
on i386, amd64, arm64, powerpc(64) and sparc64 so that they're available
out of the box in 12.0. Does anyone have concerns or objections around
this? I've posted the corresponding change here:
https://reviews.freebsd.org/D15465