* refactor(fakes): clean up add_terminal_input
* refactor(fakes): append whole buf to output_buffer in FakeStdoutWriter::write
* refactor(fakes): append whole buf to output_buffer in FakeInputOutput::write_to_tty_stdin
* fix(fakes): allow partial reads in read_from_tty_stdout
This patch fixes two bugs in read_from_tty_stdout:
* if there was a partial read (ie. `bytes.read_position` is not 0 but
less than `bytes.content.len()`), subsequent calls to would fill `buf`
starting at index `bytes.read_position` instead of 0, leaving range
0..`bytes.read_position` untouched.
* if `buf` was smaller than `bytes.content.len()`, a panic would occur.
* refactor(channels): use crossbeam instead of mpsc
This patch replaces mpsc with crossbeam channels because crossbeam
supports selecting on multiple channels which will be necessary in a
subsequent patch.
* refactor(threadbus): allow multiple receivers in Bus
This patch changes Bus to use multiple receivers. Method `recv` returns
data from all of them. This will be used in a subsequent patch for
receiving from bounded and unbounded queues at the same time.
* refactor(channels): remove SenderType enum
This enum has only one variant, so the entire enum can be replaced with
the innards of said variant.
* refactor(channels): remove Send+Sync trait implementations
The implementation of these traits is not necessary, as
SenderWithContext is automatically Send and Sync for every T and
ErrorContext that's Send and Sync.
Previously, a config file was loaded within `start()`, and if the config
file is invalid, Zellij was supposed to show a user what's wrong with
it. However, since `start()` starts setting up its terminal with an
alternative screen buffer, neither standard output nor standard error
could display such an error.
This change intends to address this issue by making Zellij load a config
file before `start()`.
In addition, the patch also includes some refactorings:
* Redefine `from_cli_config` with `TryFrom`, which was introduced in
Rust 1.34
* Remove conditional declaration `cfg(not(test))` because `start()` now
receive a `Config` as the third argument
* Introduce [`tempfile`](https://crates.io/crates/tempfile) in order to
run tests with actual files
* Typo?: "Deserialisation" -> "Deserialization"
