feat: Add batch sell stablecoin feature flag

[infiniteflower]

Explanation

Adds an optional batchSellDestStablecoins field to bridge feature flag chain configuration. The field accepts CAIP asset types and lets clients configure destination stablecoins for batch sell flows through the existing bridge feature flag payload.

The new field is validated as CaipAssetType[], preserved when feature flags are formatted, and covered by selector, formatter, and validator tests.

References

Related to SWAPS-4437

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

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Note

Low Risk
Adds a new optional field to the bridge feature-flag validation schema; main risk is rejecting/accepting remote configs incorrectly if clients/providers send unexpected values.

Overview
Adds an optional chain-level batchSellDestStablecoins feature flag to the bridge remote config, validated as an array of CAIP asset types via ChainConfigurationSchema.

Updates selector/feature-flag formatting tests to ensure the new field is preserved when formatting chain IDs to CAIP, and adds validator test coverage for valid vs malformed batchSellDestStablecoins payloads. Also records the addition in the bridge-controller changelog.

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