Ensure we send a configure when we resize

[AlanGriffiths]

Checking against the size of the most recent buffer (impl->window_size) is mostly unnecessary and may be incorrect.

Unnecessary, as we already have logic in the scene to avoid sending idempotent resize notifications. (But when first sizing surfaces, we still check to avoid a redundant configure() that breaks some tests.)

It is incorrect when we've sent a configure() but not received a buffer with configured size.

Fixes: #3040

[codecov]

Codecov Report

Merging #3042 (6b2aa78) into main (156cc32) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #3042   +/-   ##
=======================================
  Coverage   77.70%   77.70%           
=======================================
  Files        1056     1056           
  Lines       73397    73397           
=======================================
+ Hits        57030    57033    +3     
+ Misses      16367    16364    -3     

Files Changed	Coverage Δ
...rver/frontend_wayland/wayland_surface_observer.cpp	100.00% <100.00%> (ø)

... and 4 files with indirect coverage changes

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[Saviq]

What's more, this seems to avoid an extra osk/resize/redraw on startup (visible with snap set wpe-webkit-mir-kiosk url=https://google.com/).