Refactor legacy log scanner to use reader-context delete records API

### Parent

Sub-issue of #14310.

### Background

`HoodieNativeLogDeleteBlock` now exposes the reader-context-aware API:

```java
getRecordsToDelete(HoodieReaderContext readerContext)
```

Legacy log scanner paths should be migrated to this API so delete record materialization goes through the same reader-context abstraction used by native log readers.

### Scope

- Refactor legacy log scanner code to call `HoodieNativeLogDeleteBlock#getRecordsToDelete(HoodieReaderContext readerContext)`.
- Mark `DeleteRecord[] getRecordsToDelete()` as deprecated.
- Preserve existing delete semantics and add or update focused coverage for the migrated scanner path.

### Notes

This is part of the broader LSM/native log layout work tracked by #14310.