migrations: Batch fix_has_link_attribute migration.
migrations: Batch fix_has_link_attribute migration.

This avoids risk of OOM issues on servers with relatively limited RAM
and millions of messages of history; apparently, fetching all messages
ordered by ID could be quite memory-intensive even with an iterator
usage model.

Fortunately, we have other migrations that already follow this pattern
of iterating over messages, so it's easy to borrow existing code to
make this migration run reasonably.

synicalsyntax/zulip,zulip/zulip,kou/zulip,punchagan/zulip,showell/zulip,kou/zulip,punchagan/zulip,hackerkid/zulip,andersk/zulip,brainwane/zulip,rht/zulip,punchagan/zulip,andersk/zulip,andersk/zulip,punchagan/zulip,showell/zulip,showell/zulip,shubhamdhama/zulip,zulip/zulip,brainwane/zulip,synicalsyntax/zulip,shubhamdhama/zulip,timabbott/zulip,punchagan/zulip,zulip/zulip,punchagan/zulip,timabbott/zulip,synicalsyntax/zulip,rht/zulip,rht/zulip,showell/zulip,kou/zulip,synicalsyntax/zulip,hackerkid/zulip,timabbott/zulip,brainwane/zulip,rht/zulip,kou/zulip,synicalsyntax/zulip,kou/zulip,hackerkid/zulip,zulip/zulip,timabbott/zulip,punchagan/zulip,kou/zulip,zulip/zulip,hackerkid/zulip,kou/zulip,shubhamdhama/zulip,timabbott/zulip,andersk/zulip,showell/zulip,showell/zulip,synicalsyntax/zulip,eeshangarg/zulip,brainwane/zulip,rht/zulip,eeshangarg/zulip,brainwane/zulip,eeshangarg/zulip,eeshangarg/zulip,eeshangarg/zulip,zulip/zulip,hackerkid/zulip,eeshangarg/zulip,hackerkid/zulip,hackerkid/zulip,rht/zulip,brainwane/zulip,andersk/zulip,timabbott/zulip,synicalsyntax/zulip,showell/zulip,eeshangarg/zulip,zulip/zulip,brainwane/zulip,andersk/zulip,shubhamdhama/zulip,timabbott/zulip,shubhamdhama/zulip,rht/zulip,shubhamdhama/zulip,shubhamdhama/zulip,andersk/zulip