Alex Chi Z.

it's not supported anymore and the dead code should be cleaned up, maybe cc @yliang412?

regarding the size limit, pageserver currently issues a single vectored read for aux files when generating the basebackup, and we will print a warning if the size is >= 128KB....

added tests for the core `generate_key_retention` function and ready for review :)

added timeline e2e unit tests

> So, apart from the added tests, changes since my last review are that we now use lowest_retain_lsn instead of gc_cutoff The lowest image layer is created over lowest_retain_lsn instead...

> Are we not respecting the target file size yet? Yes, not for now, this is tracked in the epic.

comments resolved and ready for review again :)

ready for review; the new commit also fixes the problem of image layer writer that it does not attempt to remove the temporary file if anything goes wrong

@arpad-m do you mind have a final look of this PR since Christian is busy + this patch has been there for too long? Thanks a lot :)

misc: - [ ] create table if not exists - [ ] more efficient insert into statements via python interface (passing string is slow)