perf: linear allocator for ReadString/ReadBinary

[ppzqh]

What type of PR is this?

perf

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

en:
zh: 使用线性分配器减少 malloc 次数，优化 ReadString/ReadBinary

Benchmark

// new
BenchmarkMain/Benchmark_unmarshal_string_fastpb
BenchmarkMain/Benchmark_unmarshal_string_fastpb-12         	11505452	        97.10 ns/op	    2128 B/op	       1 allocs/op

// old
BenchmarkMain/Benchmark_unmarshal_string_fastpb
BenchmarkMain/Benchmark_unmarshal_string_fastpb-12         	 8002330	       144.8 ns/op	    2128 B/op	       3 allocs/op

Which issue(s) this PR fixes:

[github-actions]

license-eye has checked 56 files.

Valid	Invalid	Ignored	Fixed
1	16	39	0

Click to see the invalid file list

• benchmark/benchmark.go
• benchmark/benchmark_fastpb.go
• benchmark/benchmark_fastpb_test.go
• benchmark/benchmark_gogo.go
• benchmark/benchmark_gogo_test.go
• benchmark/benchmark_golang.go
• benchmark/benchmark_golang_test.go
• benchmark/benchmark_test.go
• examples/demo.go
• fastpb.go
• fastpb_impl.go
• fastpb_impl_test.go
• protoc-gen-fastpb/generator/generator.go
• protoc-gen-fastpb/main.go
• version.go
• wire_test.go

Use this command to fix any missing license headers

```bash

docker run -it --rm -v $(pwd):/github/workspace apache/skywalking-eyes header fix

</details>

[github-actions]

license-eye has checked 56 files.

Valid	Invalid	Ignored	Fixed
1	16	39	0

Click to see the invalid file list

• benchmark/benchmark.go
• benchmark/benchmark_fastpb.go
• benchmark/benchmark_fastpb_test.go
• benchmark/benchmark_gogo.go
• benchmark/benchmark_gogo_test.go
• benchmark/benchmark_golang.go
• benchmark/benchmark_golang_test.go
• benchmark/benchmark_test.go
• examples/demo.go
• fastpb.go
• fastpb_impl.go
• fastpb_impl_test.go
• protoc-gen-fastpb/generator/generator.go
• protoc-gen-fastpb/main.go
• version.go
• wire_test.go

Use this command to fix any missing license headers

```bash

docker run -it --rm -v $(pwd):/github/workspace apache/skywalking-eyes header fix

</details>