everywhere: Add pattern matching for optionals

[robryanx]

Support matches of the form:

fn valueOrDefault(anon value: i64?) -> i64 {
    return match value {
        Some(v) => v
        None => 0
    }
}

Update the stage0 bootstrap then refactor each instance in the compiler codebase where we can now match direction on the optional instead of on the bool has_value().

[BuggieBot]

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[alimpfard]

Nice, looks good!