refactor(s3stream): in preparation for segmented recovery (#2589) (#2590)

* refacotr: remove useless param passing



* revert: "release Bytebuf allocated by WAL earlier to prevent memory fragmentation (#2341)"

This reverts commit 7b4240a.

* refactor: extract `filterOutInvalidStreams`



* refactor: extract `releaseRecords`



* refactor: rename "expectXXX" to "expectedXXX"



* refactor: extract methods



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Signed-off-by: Ning Yu <[email protected]>

Author: Chillax-0v0