base: Add warn_if_once macro

Change-Id: Ie68f3b07a35ed2e6b0eee20b3b34050542fcdc6c
Signed-off-by: Tiago Muck <tiago.muck@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18420
Reviewed-by: Brandon Potter <Brandon.Potter@amd.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Tested-by: kokoro <noreply+kokoro@google.com>

misc: Rework the logging functions.

Removed the "verbose" switch which wasn't used.

Replaced the "get(LogLevel)" function with a get for each level. The
parameter was always constant, so we can just call the right function
at the right time.

Made the "exit" behavior of panic/fatal a part of the logging
implementation so that it can be overridden, and corrected a comment
which said that both fatal and panic called ::abort().

Got rid of the printEpilogue function by reworking the print() methods.
The subclasses of Logger can now override a "log" function which takes
a composed message, letting the Logger class centralize how the message
is put together and leaving the actual output mechanism to the
subclass.

Unfortunately there wasn't a way to tell gcc that the panic/fatal
macros wouldn't return, so there needed to be an exit_helper wrapper
function which calls the actual logger exit function. That can be
marked as noreturn, unlike the virtual exit function. If the exit
function does return, the wrapper will call ::abort(), placating gcc
and ensuring that even if exit isn't implemented properly, exit_helper
will still not return. That also provides a handy default
implementation.

Change-Id: I66d0cebd59f1127db980f3b565dbdf60687d8862
Reviewed-on: https://gem5-review.googlesource.com/6263
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

misc: Rename misc.(hh|cc) to logging.(hh|cc)

These files aren't a collection of miscellaneous stuff, they're the
definition of the Logger interface, and a few utility macros for
calling into that interface (panic, warn, etc.).

Change-Id: I84267ac3f45896a83c0ef027f8f19c5e9a5667d1
Reviewed-on: https://gem5-review.googlesource.com/6226
Reviewed-by: Brandon Potter <Brandon.Potter@amd.com>
Maintainer: Gabe Black <gabeblack@google.com>