[VL][1.2] Boost regex framework holds a large memory

### Backend

VL (Velox)

### Bug description

Boost regex framework seems to hold a large memory:



### Gluten version

_No response_

### Spark version

None

### Spark configurations

_No response_

### System information

_No response_

### Relevant logs

```bash

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The report concerns large memory retention in the Boost regex framework used by the Velox backend, but names no source file, entry point, or test. Start by reproducing the reported memory behavior and tracing the Velox regex integration; done means identifying the retention cause and verifying the fix with a regression check.

Written by the indexing model from the issue text.