opt:(encoder) use std strconv.AppendInt for better performance on arm

[AsterDY]

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en: according to benchmark, strconv.AppendItn() has better performance than native implementation in alg.I64toa:

goos: darwin
goarch: arm64
pkg: github.com/bytedance/sonic/internal/encoder/alg
cpu: Apple M3 Pro
BenchmarkI64toa/sonic-1-12              48961936                22.01 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/std-1-12                329461662                3.600 ns/op           0 B/op          0 allocs/op
BenchmarkI64toa/sonic-16-12             55322376                21.48 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/std-16-12               438972664                2.730 ns/op           0 B/op          0 allocs/op
BenchmarkI64toa/sonic-256-12            55268763                21.42 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/std-256-12              205196311                5.884 ns/op           0 B/op          0 allocs/op
BenchmarkI64toa/sonic-4096-12           54943064                21.90 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/std-4096-12             207751256                5.740 ns/op           0 B/op          0 allocs/op
BenchmarkI64toa/sonic-65536-12          54216253                21.70 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/std-65536-12            175604583                6.849 ns/op           0 B/op          0 allocs/op
BenchmarkI64toa/sonic-1048576-12        53292178                22.54 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/std-1048576-12          134011879                8.747 ns/op           0 B/op          0 allocs/op
BenchmarkI64toa/sonic-16777216-12       53392560                22.75 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/std-16777216-12         136341493                9.195 ns/op           0 B/op          0 allocs/op
BenchmarkI64toa/sonic-268435456-12      47283418                24.78 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/std-268435456-12        125863491                9.415 ns/op           0 B/op          0 allocs/op
BenchmarkI64toa/sonic-4294967296-12             46340396                24.68 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/std-4294967296-12               125847438                9.580 ns/op           0 B/op          0 allocs/op
BenchmarkI64toa/sonic-68719476736-12            48397423                24.95 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/std-68719476736-12              100000000               10.32 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/sonic-1099511627776-12          48338691                24.72 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/std-1099511627776-12            100000000               11.15 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/sonic-17592186044416-12         47782588                25.10 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/std-17592186044416-12           100000000               11.25 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/sonic-281474976710656-12        50566502                24.11 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/std-281474976710656-12          100000000               11.70 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/sonic-4503599627370496-12       45584118                24.80 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/std-4503599627370496-12         96807373                12.33 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/sonic-72057594037927936-12      49537647                23.57 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/std-72057594037927936-12        95043858                12.13 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/sonic-1152921504606846976-12            49055928                25.24 ns/op            0 B/op          0 allocs/op
BenchmarkI64toa/std-1152921504606846976-12              91301910                12.96 ns/op            0 B/op          0 allocs/op

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