egl: Rewrite eglGetMscRateANGLE to avoid probes and handle multi-monitor

egl: Rewrite eglGetMscRateANGLE to avoid probes and handle multi-monitor

RRGetScreenInfo re-probes connector status, which may result in an EDID
transfer for every output, which according to Adam Jackson can be on the
order of 100ms for a single EDID block.  So our previous implementation
of this eglGetMscRateANGLE was blocking for excessive periods of time
instead of being a quick query of the refresh rate like users expect.

This changes our eglGetMscRateANGLE implementation from using
RRGetScreenInfo to RRGetScreenResourcesCurrent and RRGetCrtcInfo.
This obtains the same monitor info without re-probing connectors.

Fixes a severe performance regression in Chromium WebGL performance.

While we're re-implementing the extension, we also implement proper
multi-monitor support: if there are multiple active CRTCs, we determine
which contains the largest portion of the surface, as specified in the
EGL_ANGLE_sync_control_rate extension.

We also now report fractional refresh rates correctly rather than
rounding to the nearest Hz.

Fixes: 47526556494 ("egl/x11: implement ANGLE_sync_control_rate")
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/6996
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/7038
Reviewed-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20665>