optimize(builder): impl. buffer pool & tidy dir. hierarchy

[fumiama]

• 组包引入缓存池，性能对比如下：
  • 引入前

    goos: darwin
    goarch: arm64
    pkg: github.com/LagrangeDev/LagrangeGo/utils/binary
    BenchmarkNewBuilder128-8       3077950           397.6 ns/op       352 B/op          3 allocs/op
    BenchmarkNewBuilder128_3-8     2033238           495.8 ns/op      1376 B/op          5 allocs/op
    BenchmarkNewBuilder128_5-8     1912450           637.5 ns/op      2656 B/op          6 allocs/op
    PASS
    ok    github.com/LagrangeDev/LagrangeGo/utils/binary  5.457s

  • 引入后

    goos: darwin
    goarch: arm64
    pkg: github.com/LagrangeDev/LagrangeGo/utils/binary
    BenchmarkNewBuilder128-8      36096057            33.48 ns/op      128 B/op          1 allocs/op
    BenchmarkNewBuilder128_3-8    17918258            67.04 ns/op      384 B/op          1 allocs/op
    BenchmarkNewBuilder128_5-8    11559134           100.5 ns/op       640 B/op          1 allocs/op
    PASS
    ok    github.com/LagrangeDev/LagrangeGo/utils/binary  4.937s

• 创建entity引入字符串内联以减少内存占用
• 进一步与MiraiGo对齐目录树结构，详见各commits信息

[fumiama]

本次pr之后目录结构不会大改了，所以添加新协议啥的都可以进行。之后我会改改logger。