perf: Optimize the command encoding

[Marwes]

Not as important as IO latency but can still be a decent throughput improvement.

(Lots of variance in the benchmarks but there is still some clear improvements)

encode/pipeline         time:   [727.07 us 731.89 us 737.21 us]
                        change: [-59.635% -58.716% -57.668%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 6 outliers among 100 measurements (6.00%)
  2 (2.00%) high mild
  4 (4.00%) high severe
encode/pipeline_nested  time:   [246.61 us 249.05 us 251.81 us]
                        change: [-71.597% -70.950% -70.333%] (p = 0.00 < 0.05)
                        Performance has improved.
encode/integer          time:   [693.79 us 698.95 us 703.98 us]
                        change: [-63.633% -63.125% -62.651%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 4 outliers among 100 measurements (4.00%)
  4 (4.00%) high mild
encode/small            time:   [1.1458 us 1.1580 us 1.1701 us]
                        change: [-40.826% -39.741% -38.664%] (p = 0.00 < 0.05)
                        Performance has improved.

I could probably refactor to remove these breaking changes but for the moment...

BREAKING CHANGE

ToRedisArgs has been changed to take take an instance of RedisWrite instead of Vec<Vec<u8>>. Use the write_arg method instead of Vec::push.

impl Iterator is used which requires 1.26

iter now takes self by value instead of cloning self inside the method.

[Marwes]

cc #81

[Marwes]

If #167 is merged a breaking release is needed anyways so perhaps it is fine to use impl Iterator then as well.

[Marwes]

ping @badboy

[badboy]

I won't get to review it this week

[Marwes]

I rebased and squashed this since there was some files accidentally included and to fix the conflicts.

[badboy]

I rebased and squashed this since there was some files accidentally included and to fix the conflicts.

I was just about to ask :D

[badboy]

Test failures due to formatting (because I merged #167). I'm fine with merging as is and fixing afterwards.

[badboy]

Ah damn, of course this has merge conflicts now and thus will need a rebase (and resolving those conflicts).

But otherwise I would be fine with merging it now.

[Marwes]

Rebased!