* Fix(backend): Stream logs without causing OOM
Also be smarter about when to use `heapq.merge` and when to use
`itertools.chain`: If all the logs are coming from the same instance we
`chain` them, otherwise we'll `merge` them
iterator fixes:
- group wacz files by instance by suffix, eg. -0.wacz, -1.wacz, -2.wacz
- sort wacz files, and all logs within each wacz file
- chain log iterators for all log files within wacz group
- merge log iterators across wacz files in different groups
- add type hints to help keep track of iterator helper functions
- add iter_lines() from botocore, use that for line parsing for simplicity
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Co-authored-by: Ilya Kreymer <ikreymer@gmail.com>
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