gitlab: convert old REVIEWERS into GitLab's CODEOWNERS

The old REVIEWERS file was useful back in the mailing lists days, but
nowadays we use GitLab, and we tag people by using their usernames, not
email addresses.

Most of us know each other's usernames by now, but documentation like
this is not meant for us but for everyone else, so that they can talk to
us.

Let's convert the file into GitLab's CODEOWNERS format, which maps files
in the repository to GitLab users that people can look up or tag in
their issues or merge requests.

See also: https://docs.gitlab.com/ce/user/project/code_owners.html

Signed-off-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/2178>

CODEOWNERS

@@ -0,0 +1,107 @@
+# This file contains the GitLab handle of the maintainers/reviewers for
+# a given file:
+# https://docs.gitlab.com/ce/user/project/code_owners.html
+#
+# Consider these as the list of people who want to be involved in MRs
+# touching these files/folders, and whom you can ask your questions and
+# tag in issues.
+#
+# As of GitLab 14.3, all features surrounding this file are premium-only,
+# which means this file is only read by humans for now.
+#
+# Paths starting with a `/` are relative to the git root, otherwise they
+# can match any substring of the file's path.
+# If multiple lines match, only the last one applies; there is no
+# accumulation.
+
+
+##################
+# INFRASTRUCTURE #
+##################
+
+# Build system - Meson
+meson.build @dbaker @eric
+/meson_options.txt @dbaker @eric
+/docs/meson.rst @dbaker @eric
+
+# Compatibility headers
+/include/c99* @evelikov
+/include/c11* @eric
+
+# Documentation
+/docs/ @eric @evelikov
+
+
+##########
+# COMMON #
+##########
+
+# NIR
+/src/compiler/nir/ @jekstrand
+
+# Vulkan
+/src/vulkan/ @eric @jekstrand
+/include/vulkan/ @eric @jekstrand
+
+
+#############
+# PLATFORMS #
+#############
+
+# EGL
+/src/egl/ @eric @evelikov
+/include/EGL/ @eric @evelikov
+
+# EGL - Android support
+/src/egl/drivers/dri2/platform_android.c @robh @tfiga
+
+# EGL - Device support
+/src/egl/drivers/dri2/platform_device.c @evelikov
+
+# EGL - Wayland support
+/src/egl/wayland/ @daniels @eric
+/src/egl/drivers/dri2/platform_wayland.c @daniels @eric
+
+# Gallium targets
+/src/gallium/targets/ @evelikov
+
+# GLX
+/src/glx/ @ajax
+/include/GL/glx* @ajax
+
+# GLVND
+/src/egl/main/eglglvnd.c @kbrenneman
+/src/egl/main/egldispatchstubs.* @kbrenneman
+/src/egl/generate/ @kbrenneman
+/src/glx/*glvnd* @kbrenneman
+
+# Haiku
+/include/HaikuGL/ @kallisti5
+/src/egl/drivers/haiku/ @kallisti5
+/src/gallium/frontends/hgl/ @kallisti5
+/src/gallium/targets/haiku-softpipe/ @kallisti5
+/src/gallium/winsys/sw/hgl/ @kallisti5
+/src/hgl/ @kallisti5
+
+# Loader - DRI/classic
+/src/loader/ @evelikov
+
+# Loader - Gallium
+/src/gallium/auxiliary/pipe-loader/ @evelikov
+/src/gallium/auxiliary/target-helpers/ @evelikov
+
+# Vulkan WSI - Display
+/src/vulkan/wsi/wsi_common_display.* @keithp
+/src/*/vulkan/*_wsi_display.c @keithp
+
+
+###########
+# Drivers #
+###########
+
+# Freedreno
+/src/gallium/drivers/freedreno/ @robclark
+
+# VMware
+/src/gallium/drivers/svga/ @brianp @charmainel
+/src/gallium/winsys/svga/ @thomash @drawat