base: add the --debug-flag to DPRINTF output with FmtFlag

base: add the --debug-flag to DPRINTF output with FmtFlag

This makes it easier to determine which messages come from which
flags when enabling multiple flags at once.

This commit covers the bulk of the debug messages, which use the DPRINTF*
family of macros. There however macros that use DTRACE to check for
enable, those will be covered in future patches.

Change-Id: I6738b18f08ccfd1e11f2874b426c1827b42e82a2
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/22004
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Tested-by: kokoro <noreply+kokoro@google.com>