feat: env directory path

[totoprayogo1916]

Description
This PR restores the ability to set a custom .env file path, which was no longer possible after #8604 due to hardcoded handling in Boot.php.

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[michalsn]

Branch 4.7 was out of sync. Please rebase when you get a chance.

[totoprayogo1916]

Branch 4.7 was out of sync. Please rebase when you get a chance.

rebased

[michalsn]

While changing the .env file path was possible, it was more complicated.

I hope this option won't be abused to store the file in insecure places. Because, before we could be quite sure, it would be changed only by people who know what they're doing. However, from the other side, this is not the first voice from the community to make things easier in this area, so I suppose this is acceptable.

Let's see what others will say. We will need a changelog entry for this. I didn't see a dedicated page for Config\Paths in the user guide, so I think that should be sufficient.