Add Balancer V2 config to pool-indexer

[AryanGodara]

Description

Update config to set up pool indexer to support both balancer v2 and/or uniswap-v3.

Changes

• Add a balancer_v2 config section: the Vault address, per-type factory lists, and a block chunk size.
• uniswap_v3 and balancer_v2 are both optional now. Add validate to check for at least one protocol and rejects duplicate factory addresses.
• Wire the balancer config through run.rs.

How to test

• cargo nextest run -p pool-indexer.
• Start the indexer with a balancer-only config — it's accepted. A config with neither protocol is rejected.

[github-actions]

This pull request has been marked as stale because it has been inactive a while. Please update this pull request or it will be automatically closed.