chore(tiering): Optimize serialization

[dranikpg]

• Simplfy TieredStorage::Stash logic by using OpManager::PrepareAndStash helper
• Don't serialize SmallBin to string, return object that can be serialized to destination buffer
• Return string_view[2] from CompactObj::GetRawString to determine size/get string copyless with small strings
• Use Listpack in SerializedMap constructor to avoid intermediate format

[romange]

pls respond to copilot comments

[dranikpg]

augment review

[augmentcode[bot]]

Sorry, Augment does not have access to the org this pull request's branch is from.

[dranikpg]

@romange PTAL at the updates