xwayland: glamor uses GL_RGB for some windows, but for depth=24 we need to use GL_RGBA for GL ES.

No rendering happens and we can see error on console:

(EE) glamor0: GL error: GL_INVALID_OPERATION in glTexSubImage2D(format = GL_RGBA, type = GL_UNSIGNED_BYTE, internalformat = GL_RGB8)
(EE) 
(EE) Backtrace:
(EE) 0: Xwayland (0x5569045e2000+0x166704) [0x556904748704]
(EE) 1: /usr/lib/dri/iris_dri.so (0x7f4575608000+0x121761) [0x7f4575729761]
(EE) 2: /usr/lib/dri/iris_dri.so (0x7f4575608000+0x13483c) [0x7f457573c83c]
(EE) 3: /usr/lib/dri/iris_dri.so (0x7f4575608000+0x13aee3) [0x7f4575742ee3]
(EE) 4: /usr/lib/dri/iris_dri.so (0x7f4575608000+0x146e9a) [0x7f457574ee9a]
(EE) 5: /usr/lib/dri/iris_dri.so (0x7f4575608000+0x146ffc) [0x7f457574effc]
(EE) 6: Xwayland (0x5569045e2000+0x652c2) [0x5569046472c2]
(EE) 7: Xwayland (0x5569045e2000+0x5e1b3) [0x5569046401b3]
(EE) 8: Xwayland (0x5569045e2000+0x5f4e9) [0x5569046414e9]
(EE) 9: Xwayland (0x5569045e2000+0xf27c8) [0x5569046d47c8]
(EE) 10: Xwayland (0x5569045e2000+0xf7812) [0x5569046d9812]
(EE) 11: Xwayland (0x5569045e2000+0xa7000) [0x556904689000]
(EE) 12: Xwayland (0x5569045e2000+0x3354f) [0x55690461554f]
(EE) 13: /usr/lib/libc.so.6 (0x7f4588524000+0x29290) [0x7f458854d290]
(EE) 14: /usr/lib/libc.so.6 (__libc_start_main+0x8a) [0x7f458854d34a]
(EE) 15: Xwayland (0x5569045e2000+0x34d85) [0x556904616d85]
(EE) 

Xephyr (even Xephyr with gles2) will not have this issue, only XWayland. To reproduce, use MESA_GL_VERSION_OVERRIDE=2.0

Related to #1288 (closed)

Screenshot of issue: