Handle auto enablement of texture LOD extension for GLSL 120

[Cleptomania]

Fixes a problem where Iris needs to inject the line for enabling the GL_ARB_shader_texture_lod extension when a shader calls the texture2DLod or texture3DLod extensions and is using GLSL 120.

[ah-OOG-ah]

What's a shader that would normally trigger this?

[Cleptomania]

Enabling advanced materials in BSL will trigger it. Can test without this PR to verify that.

[Cleptomania]

Technically this may add the extension to shaders that have already specified it, but I haven't seen a problem with ones that explicitly defined it themselves, it doesn't seem to do anything bad if you have the extension declared twice, but we'll have to see if that changes between drivers or something.

If we need to later, I can add in a regex to check for the extension already being declared, but I don't think it's needed.

[Cleptomania]

It is not technically valid GLSL 120 to write a shader that doesn't explicitly include this extension and use the functions from it, but Iris has had this patch since very early on, so there are almost certainly a good number of shaders doing it. The extension was made core in GLSL 130

[ah-OOG-ah]

Can confirm, fixes shader compilation for BSL w/advanced materials on Intel/Mesa.