Default ignore_* flags to true when tui=1

[skoriop]

Closes #1566

When the tui flag is set, we default ignore_crashes, ignore_ooms and ignore_timeouts to true.

The no_ignore_... struct members of LibfuzzerOptionsBuilder are used to distinguish between the user not using a flag and the user explicitly setting a flag to false (0) as both these cases result in the ignore_... struct member being false.

[domenukk]

I think we should instead use an enum here, maybe something something like
`rust
enum Setting {
Enabled,
Disabled,
Default,
}

or even have a `Tui` enum variant here?
Alternatively, maybe an `Option<bool>` would work?

[skoriop]

Yup, I think using Option<bool> is a much cleaner approach.

[domenukk]

Thanks! What do you think about my suggestion?

[domenukk]

Sweet, thanks!