[moetemp]

What changed?

This PR serves ReadRecords, with long polls, last-N reads and byte caps.

• A read long-polls up to 60 s. A Stream carries one payload type, so a read has no filter.
• A gap that retention or expiry left fails the read, so a Reader can't miss it. That includes an open Stream's expired log, before the next write and after it.
• to_offset and wake_only fail with stream_unsupported, since only the native server serves them.
• An offset past the newest + 1 fails with stream_offset_too_high (OUT_OF_RANGE), as after a failover, and the message says what to do. A negative offset is stream_invalid.
• With a byte cap, a page reads its entries from the Store in chunks that the bytes left size, so a small cap doesn't read a full page of large Records. A last-N read stops at 10,000 entries or 64 MiB.
• max_records counts items. A Superseded item and the Record after it stay in one page.
• A read of a closed Stream is done when it gives the last item. With no item left, it answers at once with done, and a waiting read ends with done at a close.

Depends on #216 (K6), and #218 (K7) is based on it. Review lane is the Rust reviewers.
Part of the Brook review series.

Why?

Reads are about half of the service. The long poll needs the most review time. The Redis read script came with R1, so this PR has no Redis part.

How did you test it?

cargo fmt, cargo clippy -- -D warnings (with and without features), cargo test -p temporalio-streams --all-features and cargo doc pass at this commit. The read cases also run on Redis, through the Redis crate.

[moetemp]

Closed in favor of #228, the combined branch, which has this change.