Ensure Faker::Internet.password method behavior is consistent with length parameters

[francktrouillez]

Motivation / Background

When using Faker::Interner.password, the min_length and max_length options are not always respected.

For instance, running the following snippet will give password out of the desired length range:

Faker::Internet.password(min_length: 2, max_length: 2) # => "Pa1" => 3 characters while I was expecting 2
Faker::Internet.password(min_length: 1, max_length: 1, mix_case: false) # => "9n" => 2 characters while I was expecting 1
Faker::Internet.password(min_length: 1, max_length: 1, mix_case: false, special_characters: true) # => "!5u" => 3 characters while I was expecting 1
Faker::Internet.password(min_length: 3, max_length: 3, mix_case: true, special_characters: true) # => "Y2#h" => 4 characters while I was expecting 3

This can lead to unexpected behavior when using the Faker::Internet.password method.

Changes proposed in this pull request

This PR fixes the issue by ensuring that the password generated respects the min_length and max_length options.

• This is done so by specifying the behavior of the mix_case option from the Faker::Internet.password method, which is to either force-include an uppercase letter AND a lowercase letter if set to true, or to only use lowercase letters if set to false (without enforcing the presence of a letter).
• This also removes the "force-addition" of digit, which lead to the password being one character longer than expected. I've opened a separate PR to enable or not the force-addition and the use of digits Allow to disable digits in Faker::Internet.password method #3033

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one change. Changes that are unrelated should be opened in separate PRs.
• Commit message has a detailed description of what changed and why. If this PR fixes a related issue include it in the commit message. Ex: [Fix #issue-number]
• Tests are added or updated if you fix a bug, refactor something, or add a feature.
• Tests and Rubocop are passing before submitting your proposed changes.

If you're proposing a new generator or locale:

• [ ] Double-check the existing generators documentation to make sure the new generator you want to add doesn't already exist.
• [ ] You've reviewed and followed the Contributing guidelines.

Closing notes

I'm open to any feedback or suggestions on how to improve this PR if this solution makes sense.

Thanks!