ngl: rendering issues on macOS

This is a follow-up issue on #7053 (closed) and !7978 (merged).

Rendering on macOS looks broken.

To investigate this further I conducted two experiments:

1. Apply the fix from !7978 (merged) directly on top of the erroneous commit
2. Revert changes made in !7978 (merged) and !7753 (merged) on top of main.

Direct application

I applied d8496d66, from !7978 (merged), directly on top of b154c9ca, from !7753 (merged).

That change does exposes rendering issues. Rendering is also broken when the GSK_DEBUG=full-redraw flag is set, although I do not experience flickering in the list view.

Something in !7753 (merged) made rendering break on macOS.

* 6daa53e26a : ngl: Conform to buffer offset alignment requirements (cherry-pick from !7978)
* b154c9caf4 : ngL: Use a single buffer for globals (from !7753)

This looks similar to what I see on main.

Reverting

As a second experiment I reverted d8496d66 and b154c9ca on main. A good thing is that those changes did not cause any merge conflicts :).

* 85d4e4aefa : Revert "ngL: Use a single buffer for globals"
* d547fa0701 : Revert "ngl: Conform to buffer offset alignment requirements"
*   ad9e868f5b : Merge branch 'wip/fix-a-couple-of-crashers' into 'main'

With both commits reverted, all works again and looks good.

CC @otte