[Enhancement]Add unit tests for BlockFileCache lazy-load and v2/v3 startup compatibility

### Search before asking

- [x] I had searched in the [issues](https://github.com/apache/doris/issues?q=is%3Aissue) and found no similar issues.

### Description

add unit test for BlockFileCache lazy-load and v2/v3 startup compatibility.
code location:be/test/io/cache/block_file_cache_test_meta_store.cpp

### Solution

_No response_

### Are you willing to submit PR?

- [x] Yes I am willing to submit a PR!

### Code of Conduct

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