Clarify support for plain integer streams

[DoFabien]

PR #1138 fixes a real TypeScript bug around integer PhysicalLevelTechnique.NONE, but while working on it I found that the repository is not aligned on whether plain integer streams are actually part of the supported design.

Current state:

• docs/specification.md lists integer physical techniques as SIMD-FastPFOR and Varint
• docs/encodings.md still defines Plain integer and long payloads as little-endian byte streams
• Rust supports and emits plain integer streams (PhysicalEncoder::None)
• Java integer decoding only supports FAST_PFOR and VARINT
• the generic C++ integer decoder rejects NONE, although geometry code has a partial tolerance path

So the question is: what is the intended project-wide direction here?

1. Keep plain integer streams as supported
2. Remove them from the supported design
3. Other / mixed approach

[HarelM]

Thanks for opening this issue! I'll post it in the slack channel to get more traction.
Very good and relevant questions.

[mactrem]

There are pros and cons. I would recommend keeping plain integer streams, mostly as they enable zero-copy use cases on fast networks where transcoding speed can become the bottleneck rather than transfer size.
This is also consistent with established columnar storage formats that maintain plain encodings such as Apache Parquet, BtrBlocks, Nimble.