Rename KvManager and LogManager into KvStore and LogStore

### Search before asking

- [x] I searched in the [issues](https://github.com/alibaba/fluss/issues) and found nothing similar.

### Description

There is an inconsistency between the documentation and the source code. The documentation refers to [LogStore and KvStore in the architecture](https://alibaba.github.io/fluss-docs/docs/concepts/architecture/), whereas the source code uses the terms `KvManager` and `LogManager`.

To align with the documentation and avoid confusion for users exploring the codebase, consider renaming `KvManager` and `LogManager` to `KvStore` and `LogStore`, respectively. This renaming process may be complex, as we need to ensure that the new names don't conflict with the current code.

### Willingness to contribute

- [x] I'm willing to submit a PR!