[datalog] Move DataLogReaderThread from glass to new libdatalog

[DeltaDizzy]

Currently the major DataLog backend API (reading and writing) is split between wpiutil and glass. In the interest of allowing code that wants to use these APIs to not need to link to glass and declutter wpiutil, all of those APIs are moved to a new library named "libdatalog".

[KangarooKoala]

Try doing git rebase -i 2027 and replacing pick with drop for the commits not in this PR.

If that doesn't work, try git reset --hard 92897bbc7156ece6d2433c2ecec6d3bc66bd6a9d (to reset to before the rebase) and then git rebase --onto 2027 HEAD main (to rebase while excluding the commits to main that aren't in 2027).

[PeterJohnson]

Let's make a different PR for the fs.h/cpp change. Also, this file should be updated to use the new defined values in fs.h instead of replicating those changes here.

[PeterJohnson]

I think as we're moving these headers, we should put them in either wpi/log or wpi/datalog instead of the top level wpi. wpi/log would match the namespace, but datalog would be more consistent with struct and protobuf and the library name, etc. This would avoid the risk of conflicts with wpiutil since they're in two separate source directories?

[DeltaDizzy]

Should the namespace be changed to match as well?