refactor(transaction-controller): remove existing transaction support

[matthewwalsh0]

Explanation

Removes legacy existing transaction deduplication logic from the transaction controller. Previously, addTransaction, stopTransaction, and speedUpTransaction would look up transactions by actionId and skip creating new ones if a match was found. This is no longer needed and adds unnecessary complexity.

actionId is still persisted on transaction metadata for state consistency.

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Note

Medium Risk
Changes core transaction lifecycle behavior so repeated calls with the same actionId will now create additional transactions (including cancel/speedup), which could surface duplicate approvals or retries if any callers relied on implicit deduping.

Overview
Removes legacy actionId-based “existing transaction” support across transaction lifecycle methods. addTransaction, stopTransaction, and speedUpTransaction no longer search state for a matching actionId to skip creating a new transaction, and the private #getTransactionWithActionId helper plus related tests are removed.

actionId remains persisted on TransactionMeta/AddTransactionOptions but is now documented as deprecated for deduplication only (state consistency), with corresponding docstring updates and a changelog entry.

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