This commit will make it so that the client will only report initalized when a valid selector is present in the basis

- modified the tests to be more robust
- modified wording on test to be more clear on what is being tested
- removed unnecessary check for ready event

**Requirements**

- [x] I have added test coverage for new or changed functionality
- [x] I have followed the repository's [pull request submission
guidelines](../blob/main/CONTRIBUTING.md#submitting-pull-requests)
- [x] I have validated my changes against all supported platform
versions

This PR will:
1. add the file data source to the custom fdv2 datasystem configuration
2. modify the initialization logic so it aligns with spec. Namely, we
will continue through the initializer list until we either run out of
intializers (in which case the synchronizers will try to do a valid
initialization) OR if an intializer fetched a proper basis with a
selector.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Introduces a file-based initializer and updates FDv2 to mark ready
only when an initializer provides a selector, with tests validating
initializer ordering and early completion.
> 
> - **Core**:
> - Add `file_ds_builder(paths)` returning `_FileDataSourceV2`
initializer in `ldclient/datasystem.py`; import `_FileDataSourceV2`.
> - **FDv2 Initialization Logic** (`ldclient/impl/datasystem/fdv2.py`):
> - After applying an initializer basis, set ready only if
`basis.change_set.selector` is defined; then return to proceed to
synchronizers.
> - **Tests**
(`ldclient/testing/impl/datasystem/test_fdv2_datasystem.py`):
> - Add tests ensuring initializers run until first success and stop on
first initializer that provides a selector; verify transition to
synchronizers.
> - Include file-based data source usage via `file_ds_builder` with temp
JSON files.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
04a2c53. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

The `new_feature_store` and `new_big_segment_store` methods accept a
`max_connections` parameter that has been unused since v8.

We cannot start using this parameter now as it would be a functionally
breaking change. Instead, we are opting to warn customers who might try
setting it explicitly.

fixes #386

🤖 I have created a release *beep* *boop*
---


##
[9.14.0](9.13.1...9.14.0)
(2025-12-04)


### Features

* adding data system option to create file datasource intializer
([e5b121f](e5b121f))
* adding file data source as an intializer
([#381](#381))
([3700d1d](3700d1d))


### Bug Fixes

* Add warning if relying on Redis `max_connections` parameter
([#387](#387))
([e6395fa](e6395fa)),
closes
[#386](#386)
* modified initializer behavior to spec
([064f65c](064f65c))

---
This PR was generated with [Release
Please](https://github.com/googleapis/release-please). See
[documentation](https://github.com/googleapis/release-please#release-please).

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