Python Extension and Python Environment Extension both activate when `python.useEnvironmentsExtension` defaults to false

还没有人认领这个 Issue。

## Environment data

## Repro Steps

* Install the Python extension
* Install the Python environment extension
* Set the user configuration to:

```json
"workbench.enableExperiments": false,
"python.experiments.enabled": false
```

Reload the window

## Expected behavior

* The Python and Python environment extension agree on which extension is responsible for managing environments

## Actual behavior

* Both extensions activate
* I see two Python selectors
* The `Select Python Environment` selector from the Python Environment extension is missing

## Additional context

The Python Environment Extension uses `inspect` to decide whether `useEnvironmentsExtension` is set to false, but this does not take into account a default value.

The `when` condition of the Command Palette entry uses `when`, which takes default values into account

The Python Extension uses `get`, which takes default values into account

This came up in https://github.com/astral-sh/ty-vscode/issues/551 because it's now unclear which extension ty should consider as being authoritative when it comes to selecting an environment.

先定位 Python Environment Extension 的配置检查和激活逻辑，然后将其与 Python Extension 考虑默认值的 get 行为以及 Command Palette 的 when condition 进行比较。在安装了两个扩展且禁用实验功能的情况下重现；当扩展在环境归属上达成一致，并且只显示预期的选择器时，即视为完成。

由索引模型根据 Issue 内容生成。