2D: Fix various issues and minor performance optimizations

[stuartcarnie]

Summary

This PR includes a number of important bug fixes and a performance improvement for managing the texture state and DrawData in uniform set 3.

Another important change in this PR is to move the specular_shininess to PushConstant state, allowing the field to be used for #97058.

Closing #97340 in favour of this, noting that this PR will not address font rendering improvements, which will require separate work. It does improve the performance of text rendering of the test in this comment from 40 fps to 76 fps, due to the minor CPU optimisations included in this PR.

Bugfixes

• As noted in this comment, fixes Successive calls to CanvasItem.draw_primitive() disregard the texture #97586 for the forward+ renderer, but not compatibility
• Closes Vertex colors are assigned incorrectly in quadrilaterals drawn using CommandPrimitive #97593 which is a forward+ issue only
• Fixes NormalMaps are weird in 4.4-dev3 #97774
• Fixes Debug CanvasItem Redraw is not available #98005

[clayjohn]

Code looks great and I am able to reproduce the performance improvement in CPU-bound scenarios.

[Repiteo]

Thanks!