Add split and split_once to bit_array module

[ackurat]

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Hello, This PR solves issue #568 and also adds a split function. Both split and split_once functions as their counterparts in the the gleam/string module, and have feature parity across the targets.

There are two older PRs (#571, #629) which addresses this, but they seem to be outdated/abandoned.

The split function could take options to make it have feature parity with Erlang's binary:split/3, but I opted for a simpler version here. Let me know if you'd like me to add the options feature.