WIP: perf(codec): optimize performance

[lsjbd]

What type of PR is this?

perf

What this PR does / why we need it (en: English/zh: Chinese):

en: improve the performance of TTHeader codec
zh: 优化 TTHeader 编解码的性能

Which issue(s) this PR fixes:

[lsjbd]

Benchamrks comparation:

name                             old time/op    new time/op    delta
TTHeaderCodec-8                    4.35µs ± 2%    3.94µs ± 3%   -9.55%  (p=0.000 n=9+10)
TTHeaderWithTransInfoParallel-8    11.3µs ± 8%     9.7µs ± 5%  -14.58%  (p=0.000 n=10+10)
TTHeaderCodecParallel-8            5.35µs ± 5%    4.93µs ± 3%   -7.88%  (p=0.000 n=10+9)

name                             old alloc/op   new alloc/op   delta
TTHeaderCodec-8                    1.30kB ± 0%    0.95kB ± 0%  -27.05%  (p=0.000 n=10+10)
TTHeaderWithTransInfoParallel-8    2.12kB ± 0%    1.57kB ± 0%  -25.67%  (p=0.000 n=10+10)
TTHeaderCodecParallel-8            1.30kB ± 0%    0.95kB ± 0%  -27.05%  (p=0.000 n=10+10)

name                             old allocs/op  new allocs/op  delta
TTHeaderCodec-8                      19.0 ± 0%      16.0 ± 0%  -15.79%  (p=0.000 n=10+10)
TTHeaderWithTransInfoParallel-8      38.0 ± 0%      35.0 ± 0%   -7.89%  (p=0.000 n=10+10)
TTHeaderCodecParallel-8              19.0 ± 0%      16.0 ± 0%  -15.79%  (p=0.000 n=10+10)

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