scons: Separate debug flags from debug-format flags

scons: Separate debug flags from debug-format flags

Debug flags are flags that aid with debugging by printing
relevant information when enabled. Debug-formatting flags
define how the debug flags will print the information.

Although a viability, this patch does not support declaring
compound format flags.

As a side effect, now debug flags and debug-formatting flags
are printed in different lists, when using --debug-help.

Change-Id: Ieae68745276218cf4e9c1d37d7bf3bd1f19709ae
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/39076
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>