contracts: Fix printing the `Schedule` (#3021)

Printing the `Schedule` is a useful debugging tool and general sanity
check. It is much more easy to interpret than the raw weights.

The printing relied on using `println` and hence was only available from
the native runtime. This is no longer available. This is why in this PR
we switch to using `log` which works from Wasm.

I made sure that the `WeightDebug` is only derived when
`runtime-benchmarks` is set so that we don't increase the size of the
binary.

Some other changes were necessary to make this actually work inside the
runtime. For example, I needed to remove `format!` and usage of floats.

Please note that this removed the decimal from the number because
truncating the fraction without using floats would not be easy and would
require custom code. I think the precision here is sufficient.

This is how the output looks like now:
```
Schedule {
    limits: Limits {
        event_topics: 4,
        globals: 256,
        locals: 1024,
        parameters: 128,
        memory_pages: 16,
        table_size: 4096,
        br_table_size: 256,
        subject_len: 32,
        payload_len: 16384,
        runtime_memory: 134217728,
    },
    instruction_weights: InstructionWeights {
        base: 2565,
        _phantom: PhantomData<kitchensink_runtime::Runtime>,
    },
    host_fn_weights: HostFnWeights {
        caller: 322 ns, 6 bytes,
        is_contract: 28 µs, 2684 bytes,
        code_hash: 29 µs, 2688 bytes,
        own_code_hash: 400 ns, 6 bytes,
        caller_is_origin: 176 ns, 3 bytes,
        caller_is_root: 158 ns, 3 bytes,
        address: 315 ns, 6 bytes,
        gas_left: 355 ns, 6 bytes,
        balance: 1 µs, 6 bytes,
        value_transferred: 314 ns, 6 bytes,
        minimum_balance: 318 ns, 6 bytes,
        block_number: 313 ns, 6 bytes,
        now: 325 ns, 6 bytes,
        weight_to_fee: 1 µs, 14 bytes,
        input: 263 ns, 6 bytes,
        input_per_byte: 989 ps, 0 bytes,
        r#return: 0 ps, 45 bytes,
        return_per_byte: 320 ps, 0 bytes,
        terminate: 1 ms, 5266 bytes,
        random: 1 µs, 10 bytes,
        deposit_event: 1 µs, 10 bytes,
        deposit_event_per_topic: 127 µs, 2508 bytes,
        deposit_event_per_byte: 501 ps, 0 bytes,
        debug_message: 226 ns, 7 bytes,
        debug_message_per_byte: 1 ns, 0 bytes,
        set_storage: 131 µs, 293 bytes,
        set_storage_per_new_byte: 576 ps, 0 bytes,
        set_storage_per_old_byte: 184 ps, 1 bytes,
        set_code_hash: 297 µs, 3090 bytes,
        clear_storage: 131 µs, 289 bytes,
        clear_storage_per_byte: 92 ps, 1 bytes,
        contains_storage: 29 µs, 289 bytes,
        contains_storage_per_byte: 213 ps, 1 bytes,
        get_storage: 29 µs, 297 bytes,
        get_storage_per_byte: 980 ps, 1 bytes,
        take_storage: 131 µs, 297 bytes,
        take_storage_per_byte: 921 ps, 1 bytes,
        transfer: 156 µs, 2520 bytes,
        call: 484 µs, 2721 bytes,
        delegate_call: 406 µs, 2637 bytes,
        call_transfer_surcharge: 607 µs, 5227 bytes,
        call_per_cloned_byte: 970 ps, 0 bytes,
        instantiate: 1 ms, 2731 bytes,
        instantiate_transfer_surcharge: 131 µs, 2549 bytes,
        instantiate_per_input_byte: 1 ns, 0 bytes,
        instantiate_per_salt_byte: 1 ns, 0 bytes,
        hash_sha2_256: 377 ns, 8 bytes,
        hash_sha2_256_per_byte: 1 ns, 0 bytes,
        hash_keccak_256: 767 ns, 8 bytes,
        hash_keccak_256_per_byte: 3 ns, 0 bytes,
        hash_blake2_256: 443 ns, 8 bytes,
        hash_blake2_256_per_byte: 1 ns, 0 bytes,
        hash_blake2_128: 440 ns, 8 bytes,
        hash_blake2_128_per_byte: 1 ns, 0 bytes,
        ecdsa_recover: 45 µs, 77 bytes,
        ecdsa_to_eth_address: 11 µs, 42 bytes,
        sr25519_verify: 41 µs, 112 bytes,
        sr25519_verify_per_byte: 5 ns, 1 bytes,
        reentrance_count: 174 ns, 3 bytes,
        account_reentrance_count: 248 ns, 40 bytes,
        instantiation_nonce: 154 ns, 3 bytes,
        add_delegate_dependency: 131 µs, 2606 bytes,
        remove_delegate_dependency: 130 µs, 2568 bytes,
    },
}
###############################################
Lazy deletion weight per key: Weight(ref_time: 126109302, proof_size: 70)
Lazy deletion keys per block: 15859
```