fix: Move gasless flag to extended pay config

[pedronfigueiredo]

What changed

• Moved the Relay execute toggle to confirmations_pay_extended.payStrategies.relay.gaslessEnabled.
• Renamed the flag back to gaslessEnabled and removed transaction-pay-controller source/test references to isGaslessEnabled.
• Updated feature flag tests for the new remote flag namespace.
• Updated the transaction-pay-controller changelog entry to reference this PR.

Why

This keeps confirmations_pay available for the existing release-scoped flag while allowing the new release behavior to be controlled from confirmations_pay_extended.

Validation

• yarn workspace @metamask/transaction-pay-controller run jest --no-coverage src/utils/feature-flags.test.ts
• yarn workspace @metamask/transaction-pay-controller run test
• yarn workspace @metamask/transaction-pay-controller run changelog:validate
• yarn build

---

Note

Medium Risk
Medium risk because it changes the remote feature-flag lookup path/name that gates the Relay /execute gasless flow; misconfiguration could unintentionally enable/disable gasless execution.

Overview
Updates the Relay gasless execute toggle to read from remoteFeatureFlags.confirmations_pay_extended.payStrategies.relay.gaslessEnabled (renaming from isGaslessEnabled and removing the old confirmations_pay location).

Adjusts isRelayExecuteEnabled unit tests to match the new namespace/key, and updates the changelog to document the flag move.

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[matthewwalsh0]

I thought we only used this property currently?

[cursor]

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