feature: Add modern streaming API (without using `reflect` package)

[fxamacker]

Obsoletes #291

Rather than migrating the old feature/stream-mode API into main branch, I will be implementing a new streaming API with a more user-friendly API and modern implementation.

Currently, this CBOR codec uses Go's built-in reflect package. Although feature/stream-mode branch avoids using reflect package, using the stream-mode branch requires detailed knowledge of RFC 8949.

The new stream-mode API will provide the performance of feature/stream-mode while being more user-friendly to programmers who don't have detailed knowledge of RFC 8949.

Also, programs using the new streaming API benefit from improved compatibility with TinyGo compiler.

The upcoming encoding/json/v2 has some great ideas and I would like to avoid reinventing the wheel when it makes sense, but CBOR has more features (e.g., CBOR tags) and a more extensive data model than JSON so there will be differences.

I will open a discussion about the API after working out a few more details in a proof-of-concept I've been exploring during weekends.

There are a handful of open issues this can address and I will link this issue to them after we have public discussions about the new streaming API.

Notes

This weekend (July 20), I stumbled across an old comparison (both benchmarks use this library).

This comparison shows standard API (enc.Encode) is slower vs old streaming API of this library.

name                     time/op        alloc/op      allocs/op
UintWriteCbor-8          69.1ns ± 0%    19.0B ± 0%       0
UintStreamWriteCbor-8    10.1ns ± 1%    16.0B ± 0%       0

* Go 1.17 linux_amd64 (Haswell Xeon)

[fxamacker]

I just stumbled across this very old comparison today (Sunday, July 20, 2025).

This shows standard API (enc.Encode) is significantly slower than the old streaming API of this library.

name                     time/op        alloc/op      allocs/op
UintWriteCbor-8          69.1ns ± 0%    19.0B ± 0%       0
UintStreamWriteCbor-8    10.1ns ± 1%    16.0B ± 0%       0

* Go 1.17 linux_amd64 (Haswell Xeon)