Various linux fixes

[raphaelthegreat]

Mostly a collection of fixes for linux that I had in the present branch but that might take a while to merge so having these here.

• Fix a build error regarding boost asio placeholders. Seems like using std placeholders works fine so do that instead.
• Disable SDL pipewire backend as I found it to cause crackly audio in certain games like BB Alpha
• Rework TLS emulation to use GS segment instead of trampolines. This should eliminate all TLS related assertions on linux platforms.
• Actually properly implement case insensitive search. This has been quite annoying for a while so time to get it out of the way. When a path does not exist, it looks for the parent path until one is found and then traverses the folders in case any of them exist with different case. There is also a lookup cache for paths that should speed things up if e.g a lot of files are accessed in the same miscased folder
• While not related to linux, switched num_submits back to std::atomic as its written without a lock protection and I have found some cases where this leads to a deadlock