Related #10708
# Description
Add `bytes split` command. `bytes split` splits its input on the
provided separator on binary values _and_ binary streams without
collecting. The separator can be a multiple character string or multiple
byte binary.
It can be used when neither `split row` (not streaming over raw input)
nor `lines` (streaming, but can only split on newlines) is right.
The backing iterator implemented in this PR, `SplitRead`, can be used to
implement a streaming `split row` in the future.
# User-Facing Changes
`bytes split` command added, which can be used to split binary values
and raw streams using a separator.
# Tests + Formatting
- 🟢 toolkit fmt
- 🟢 toolkit clippy
- 🟢 toolkit test
- 🟢 toolkit test stdlib
# After Submitting
Mention in release notes.
