controlled indexing after migration

[LexLuthr]

This PR makes the following changes to the market migration.

1. The indexing tasks are no longer created directly.
2. All info is captured in a table market_mk12_deal_pipeline_migration
3. A migration function is called every 30 seconds by market poller to migrate data from this table to mk12_pipeline table which in turn creates indexing tasks along with IPNI if required.
4. The function has following logic:
   • Step 1: Check if the migration table has entries
   • Step 2: Count entries ready for indexing in the pipeline table
   • Step 3: Count pending IPNI tasks
   • Calculate how many entries we need to reach 16
   • Calculate how many entries we can move without exceeding 16 pending IPNI tasks
   • Limit by the number of entries available in the migration table
   • Move entries from the migration table to the pipeline table

Relevant changes in Boost will be done.

[magik6k]

This looks basically good, couple small nits, but this already should work

[magik6k]

I don't quite understand what the purpose of this is. Just being careful around retry?

[LexLuthr]

Yes. Being extra careful.