fmt::join was moved into fmt/ranges.h

Signed-off-by: Alfred Wingate <parona@protonmail.com>

Eliminate SettingsHandler's `SetBytes` and `Reset` methods

Also make the `Decrypt` method private.

As far as I can tell, the only motivation for exposing the `SetBytes`
and `Reset` methods is to allow `CBoot::SetupWiiMemory` to use the same
`SettingsHandler` instance to read settings data and then write it back.
It seems cleaner to just use two separate instances, and require a given
`SettingsHandler` instance to be used for either writing data to a
buffer or reading data from a buffer, but not both.

A natural next step is to split the `SettingsHandler` class into two
classes, one for writing data and one for reading data. I've deferred
that change for a future PR.

Use 1 of the same type as the stored value when shifting left. This
prevents undefined behavior caused by shifting an int more than 31 bits.

Previously iterator incrementation could either hang or prematurely
report it had reached the end of the bitset.

Group numbers and their bitcounts together in pairs, which allows for
range-based loop iteration.