docs: update references for generic buffer API

[hayabusa-cloud]

Summary

Update documentation and benchmark names to reflect the generic functions introduced in #9.

Changes

• Replace IoVecFromSmallBuffers with IoVecFrom in README examples
• Update API listing in READMEs to show IoVecFrom[T BufferType] generic signature
• Fix doc.go example to use IoVecFrom
• Rename benchmark functions to match generic naming (BenchmarkIoVecFrom_SmallBuffer_8, etc.)

Test plan

• go vet ./... clean
• go test -race ./... passes

[codecov]

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✅ All modified and coverable lines are covered by tests.

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[Copilot]

Pull request overview

This PR updates all documentation and benchmark names to reflect the generic buffer API introduced in PR #9, which replaced 36 type-specific functions with 3 generic functions using Go's BufferType constraint. The changes ensure that examples, API listings, and benchmark names accurately represent the new IoVecFrom[T BufferType] generic function.

Changes:

• Updated code examples across all documentation files to use IoVecFrom instead of IoVecFromSmallBuffers
• Added generic function signature IoVecFrom[T BufferType](buffers []T) []IoVec to API listings in all README files
• Renamed benchmark functions to follow new naming convention (e.g., BenchmarkIoVecFrom_SmallBuffer_8)

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
doc.go	Updated package documentation example to use generic IoVecFrom function
benchmark_test.go	Renamed benchmark functions from BenchmarkIoVecFromSmallBuffers_* to BenchmarkIoVecFrom_SmallBuffer_* pattern
README.md	Updated English documentation with generic API signature and example usage
README.zh-CN.md	Updated Chinese documentation with generic API signature and example usage
README.ja.md	Updated Japanese documentation with generic API signature and example usage
README.fr.md	Updated French documentation with generic API signature and example usage
README.es.md	Updated Spanish documentation with generic API signature and example usage