misc: Add the magic_enum.hh external header (v0.9.2)

Also increase maximum enum supported value to 0x100

This library is courtesy of Daniil Goncharov and hosted at
https://github.com/Neargye/magic_enum/tree/master. It enables
compile-time and runtime string to/from enum value conversion as well
as other fancy enum introspection-like things.

The MIT lincence should not conflict with gem5 in any way.

Copying the file for now but a submodule might be more suitable if
gem5 uses them in the future.

Change-Id: Ib0c8f943b79c703f1247c11c7291fb4fb1548b0f
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/67665
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>

ext/magic_enum/SConscript

@@ -0,0 +1,37 @@
+# Copyright (c) 2022 Arteris, Inc. and its applicable licensors and affiliates.
+# All rights reserved.  This license is licensed under the Gem5 license.
+#
+# The license below extends only to copyright in the software and shall not be
+# construed as granting a license to any other intellectual property including
+# but not limited to intellectual property relating to a hardware
+# implementation of the functionality of the software licensed hereunder.  You
+# may use the software subject to the license terms below provided that you
+# ensure that this notice is replicated unmodified and in its entirety in all
+# distributions of the software, modified or unmodified, in source code or in
+# binary form.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+# redistributions of source code must retain the above copyright notice, this
+# list of conditions and the following disclaimer; redistributions in binary
+# form must reproduce the above copyright notice, this list of conditions and
+# the following disclaimer in the documentation and/or other materials provided
+# with the distribution; neither the name of the copyright holders nor the
+# names of its contributors may be used to endorse or promote products derived
+# from this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+
+Import('env')
+
+env.Append(CPPDEFINES=['MAGIC_ENUM_RANGE_MAX=0x100'])