Improve vault endpoint performance. (backport #2475)

[mergify]

Changelist

Fetch funding index update maps in bulk rather than one at a time per vault.

Test Plan

Unit tests.

Author/Reviewer Checklist

• If this PR has changes that result in a different app state given the same prior state and transaction list, manually add the state-breaking label.
• If the PR has breaking postgres changes to the indexer add the indexer-postgres-breaking label.
• If this PR isn't state-breaking but has changes that modify behavior in PrepareProposal or ProcessProposal, manually add the label proposal-breaking.
• If this PR is one of many that implement a specific feature, manually label them all feature:[feature-name].
• If you wish to for mergify-bot to automatically create a PR to backport your change to a release branch, manually add the label backport/[branch-name].
• Manually add any of the following labels: refactor, chore, bug.

Summary by CodeRabbit

• New Features

  • Introduced a new method to retrieve funding index maps for multiple effective heights, enhancing data retrieval capabilities.

• Bug Fixes

  • Optimized the getVaultPositions function for improved performance in fetching funding index maps.

• Documentation

  • Updated method signatures and interfaces for better clarity and usability.

• Refactor

  • Streamlined data retrieval logic in the VaultController to enhance efficiency and readability.

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This is an automatic backport of pull request #2475 done by [Mergify](https://mergify.com).