Improve compat by temporarily suspending shaders while another mod uses the vanilla ShaderManager

[Johni0702]

Albedo might want to suspend its shaders while another mod tries to use the vanilla ShaderManager. E.g. BetterPortals uses the ShaderManager to render its portal framebuffers into the world: https://github.com/Johni0702/BetterPortals/blob/398e594e6e3bad62d52a91fd838e676dd4971f64/src/api/kotlin/de/johni0702/minecraft/betterportals/client/render/PortalRenderer.kt#L85-L108
Possibly related: Johni0702/BetterPortals#461

Note: I've reported this to HRZN back in July when their issue tracker was the one linked on CurseForge. Three months later I've got the reply that they're no longer working on Albedo and that I should report issues to the new maintainer (at which point the issue tracker on CF was still linking to them), so today Albedo came up again in a bug report on one of my mods, I noticed the new issue tracker and figured I might as well re-report those issues.
Thing is, I see no way to access my old reports (except the title which I got in the reply email) and don't recall exactly what they were about, so feel free to ask for details if my description is too short and I'll have another look at the code.