feat(transaction-pay): add Across strategy support

[pedronfigueiredo]

Explanation

This PR extracts the Across strategy work on top of the provider-fallback baseline.

It adds:

• Across strategy wiring (across strategy type + registration)
• Across quote retrieval/parsing/normalization
• Across submit flow for approval + swap/deposit execution paths
• Across-specific types/constants required for compilation
• Minimal selection/config hooks to make Across selectable
• Changelog entries for transaction-controller and transaction-pay-controller

References

Addresses: https://github.com/MetaMask/MetaMask-planning/issues/6997

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

Medium Risk
Introduces a new cross-chain quoting/submission path that constructs and submits approval + swap/deposit transactions and relies on remote feature-flag configuration and external API responses, which could affect transaction execution if misconfigured or parsed incorrectly.

Overview
Adds Across as a new TransactionPayStrategy and wires it into strategy selection/ordering (defaulting to Relay then Across), with config driven by remote feature flags.

Implements the Across integration end-to-end: fetches/normalizes quotes from the Across API (slippage, fees/impact, gas estimates with buffering/fallback, optional API keys/app fees, and optional embedded “actions” for delegation flows) and submits quotes by creating either a transaction batch (ERC20 approvals + deposit) or a single swap/deposit tx.

Extends types to support quote impact/impactRatio and reusable action payloads, introduces estimateGasWithBufferOrFallback, and adds new TransactionTypes (perpsAcrossDeposit, predictAcrossDeposit) used when submitting Across deposits for Perps/Predict. Changelogs and tests are updated accordingly.

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