Draft: Update all the deps

Updates an absurd amount of dependencies, notably:

• Rust stable version (I build using nightly with no problems) to 1.68.0
• rocksdb to latest version (0.20.1) and only enables important features instead of building all of them (some of which is not needed and was not used previously). default-features = false, features = ["multi-threaded-cf", "zstd", "snappy", "lz4", "zlib"]
• Bump ruma commit to https://github.com/ruma/ruma/commit/4d40623ae426fe44ffb7d93ffe7f3e34c4e7870a (couldn't update beyond that without a bunch of changes that are beyond me 😅 ). Couple things were renamed / moved around but functionally the same

Currently using all of these changes on my personal build with no problems, including adding a new user, resetting password, basic moderation actions, and in a lot of complex rooms.

Did not touch stuff like other DB backends as I only use rocksdb and cannot test those.

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• I agree to release my code and all other changes of this MR under the Apache-2.0 license