Add timeout

[bjorn3]

To bisect hangs.

[Mark-Simulacrum]

Timeout to what? What hangs? Can you provide more clarification?

[bjorn3]

If the rustc regression is a hang, it would be useful for cargo-bisect-rustc to timeout after testing for a certain amount of time and then considering that timeout as if the compiler crashed.

[bjorn3]

For context: I was trying to bisect rust-lang/rust#72051.

[hkratz]

Quite a few "extreme" slowness / hang issues lately where that would help do an unattended bisect instead of using --prompt.

[ehuss]

This is now implemented via #135 and should be in the recently published 0.6.1. Feel free to open new issues if there are any problems with the new --timeout option.