sim-cli: remove broken parser for activity multiplier

[carlaKC]

u64 parser does not work for a f64 value.

Broken on main:

sim-cli sim.json
thread 'main' panicked at 'Mismatch between definition and access of `capacity_multiplier`. Could not downcast to TypeId { t: 8711759054683223602271599665973969982 }, need to downcast to TypeId { t: 25882202575019293479932656973818029271 }
', /Users/carla/.cargo/registry/src/index.crates.io-6f17d22bba15001f/clap_builder-4.4.6/src/parser/error.rs:32:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

sim-cli sim.json --capacity-multiplier 0.5
error: invalid value '0.5' for '--capacity-multiplier <CAPACITY_MULTIPLIER>': invalid digit found in string

[okjodom]

lgtm. we could replace this with a custom value parser

[sr-gi]

Oh damn, my bad :(

We can use a StringValueParser with try_map to fix this.

#[clap(long, short, default_value_t = ACTIVITY_MULTIPLIER, value_parser = clap::builder::StringValueParser::new().try_map(|x| {
    match x.parse::<f64>() {
        Ok(x) => {
            if x > 0.0 {
                Ok(x)
            } else {
                Err(format!("capacity_multiplier must be higher than 0. {x} received."))
            }
        },
        Err(e) =>  {
            Err(e.to_string())
        }
    }   
}))]

Notice this does not have to be inlined, we can define a function elsewhere and jut pass it to try_map