[3.x] Fix various GCC 13 warnings

[akien-mga]

Fixes occurrences of -Wtype-limits, -Wmaybe-uninitialized, -Wduplicated-branches.

Includes 3.x version of #85500.

[AThousandShips]

LGTM, makes sense

[akien-mga]

Added some more warning fixes.

This doesn't yet allow building 3.x with GCC 13.2.0 warning free, as I ran into this more complex one:

In file included from drivers/gles2/rasterizer_canvas_gles2.h:34,
                 from drivers/gles2/rasterizer_canvas_gles2.cpp:31:
In member function 'RasterizerCanvasBatcher<T, T_STORAGE>::Batch* RasterizerCanvasBatcher<T, T_STORAGE>::_batch_request_new(bool) [with T = RasterizerCanvasGLES2; T_STORAGE = RasterizerStorageGLES2]',
    inlined from 'void RasterizerCanvasBatcher<T, T_STORAGE>::_prefill_default_batch(FillState&, int, const RasterizerCanvas::Item&) [with T = RasterizerCanvasGLES2; T_STORAGE = RasterizerStorageGLES2]' at ./drivers/gles_common/rasterizer_canvas_batcher.h:891:48,
    inlined from 'void RasterizerCanvasBatcher<T, T_STORAGE>::_prefill_default_batch(FillState&, int, const RasterizerCanvas::Item&) [with T = RasterizerCanvasGLES2; T_STORAGE = RasterizerStorageGLES2]' at ./drivers/gles_common/rasterizer_canvas_batcher.h:844:1:
./drivers/gles_common/rasterizer_canvas_batcher.h:689:31: error: 'void* memset(void*, int, size_t)' offset [0, 29] is out of the bounds [0, 0] [-Werror=array-bounds=]
  689 |                         memset(batch, 0, sizeof(Batch));
      |                         ~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
In member function 'RasterizerCanvasBatcher<T, T_STORAGE>::Batch* RasterizerCanvasBatcher<T, T_STORAGE>::_batch_request_new(bool) [with T = RasterizerCanvasGLES2; T_STORAGE = RasterizerStorageGLES2]',
    inlined from 'void RasterizerCanvasBatcher<T, T_STORAGE>::_prefill_default_batch(FillState&, int, const RasterizerCanvas::Item&) [with T = RasterizerCanvasGLES2; T_STORAGE = RasterizerStorageGLES2]' at ./drivers/gles_common/rasterizer_canvas_batcher.h:917:47,
    inlined from 'void RasterizerCanvasBatcher<T, T_STORAGE>::_prefill_default_batch(FillState&, int, const RasterizerCanvas::Item&) [with T = RasterizerCanvasGLES2; T_STORAGE = RasterizerStorageGLES2]' at ./drivers/gles_common/rasterizer_canvas_batcher.h:844:1:
./drivers/gles_common/rasterizer_canvas_batcher.h:689:31: error: 'void* memset(void*, int, size_t)' offset [0, 29] is out of the bounds [0, 0] [-Werror=array-bounds=]
  689 |                         memset(batch, 0, sizeof(Batch));
      |                         ~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

GCC seems to disagree with @lawnjelly's comment:

			// this should always succeed after growing
			batch = bdata.batches.request();
			RAST_DEBUG_ASSERT(batch);

(that RAST_DEBUG_ASSERT is a no-op in release builds, and batch is used later without checking if it's nullptr)

[akien-mga]

Ok, done. Aside from the warning in RasterizerCanvasBatcher, the 3.x branch now compiles warning free with both tools=yes target=release_debug dev=yes and tools=no target=release dev=yes.

Might be some other warnings in some other tools/target/optimization configs but that's a good pass already.

[lawnjelly]

GCC seems to disagree with @lawnjelly's comment:
// this should always succeed after growing

My comment should probably more accurately be:
// this should always succeed after growing UNLESS OUT OF MEMORY AND WORLD IS ENDING

[akien-mga]

Cherry-picked for 3.5.4.