Accept CRLF delimiters in NDJSON sync streams

[birdmanmandbir]

What changed

• Accept CRLF alongside LF when splitting text sync-stream lines.
• Preserve carriage returns that are payload data rather than part of a CRLF delimiter.
• Cover a CRLF delimiter split across source chunks and a regular CRLF delimiter.

Root cause

LineSplitter removed the LF byte but forwarded the CR byte from a CRLF delimiter. NDJSON 1.0 permits CRLF and requires parsers to accept it.

Validation

• cargo fmt --all --check
• cargo test -p powersync accepts_crlf_delimiters_without_stripping_other_carriage_returns --all-features
• cargo test --workspace --all-features
• cargo clippy -p powersync --all-targets -- -D warnings

No separate issue: this is a small standards-compliance fix with a deterministic regression.

[simolus3]

This is not a general-purpose ndjson decoder, it only needs to decode lines from the PowerSync service. The service will never include CRLF line endings.