Performance regression in ThrottleAccumulator

### Description

Calling `getAutoAssociationsCount()` from `ThrottleAccumulator.shouldThrottleTxn()` (introduced by #13909) causes a severe performance regression due to #10998.
Adding disk operations to a critical section creates contention between `netty` threads and reduces TPS.

### Steps to reproduce

Run `NftTransferLoadTest` in single-node mode.

### Additional context

_No response_

### Hedera network

_No response_

### Version

0.53.0

### Operating system

Linux

Start with ThrottleAccumulator.shouldThrottleTxn() and its call to getAutoAssociationsCount(), then reproduce the regression with NftTransferLoadTest in single-node mode. Review the context from #13909 and #10998; done means removing the critical-section contention and restoring expected transaction throughput without changing throttling behavior.

Written by the indexing model from the issue text.