Fetch uncached V3 pools on demand so cold quotes find liquidity

[AryanGodara]

Description

The driver's Uniswap V3 fetcher warm-caches the top max-pools-to-initialize pools ranked by raw liquidity. Raw liquidity isn't comparable across pools (it scales with token decimals and price range), so well-funded pools with a low raw value are excluded from the warm cache. When a quote requests such a pair, checkpoint.get() returns nothing and fetch returns zero AMMs, failing the quote until a later maintenance tick happens to back-fill the pool.

This change makes fetch fetch the requested pairs' uncached pools on demand instead of deferring to maintenance, so the first quote for any pair finds liquidity.

Changes

• PoolsCheckpointHandler::get also returns the ids of pools that exist for the requested pairs but aren't cached.
• fetch fetches those on demand (new fetch_pools) before building the result; on failure it serves whatever is cached.
• fetch_pools skips pools whose conversion fails (e.g. ticks not yet available) instead of aborting the batch; update_missing_pools reuses it, so periodic maintenance gains the same resilience.
• Unit tests for the on-demand path and the skip-on-failure behaviour.

Stacked on #4559 (bootstrap split) and #4555 (migration isolation) so one image carries all three for combined staging validation.

How to test

Unit + e2e tests.
Did a local driver against an ink-seeded pool-indexer. it loads the previously-missing pools on the first quote.