backends/drm: refactor drm property handling

Merged Xaver Hugl requested to merge work/zamundaaa/drm-properties into master

Commit 1: drop some logging. We're using drm_info for all this stuff now, the logging isn't really useful anymore

Commit 2: instead of storing DrmProperty in a vector per object with enums for accessing the correct one, store them directly as values. This reduces the amount of typing needed to access the properties and makes it possible to handle enums in a more type safe way

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