Fix regex dot/backslash issue

[krsriq]

What is the reason for this PR?

There are two bugs in regexify that make #134 fail: when regexify is called with a dot (matches any character in regex), the dot may get replaced (by asciify) with a backslash, which is an escape character:

Faker/src/Faker/Provider/Base.php

Line 533 in c65e3b6

$regex = preg_replace_callback('/(?<!\\\)\./', 'static::randomAscii', $regex);

Secondly, all backslashes are removed - even the ones that are escaped:

Faker/src/Faker/Provider/Base.php

Line 535 in c65e3b6

$regex = str_replace('\\', '', $regex);

• Fixed an issue
• Covered by tests

Author's checklist

• Follow the Contribution Guide
• New features and changes are documented

Summary of changes

This PR fixes the issues by checking whether asciify returns a backsash. In case it does it adds another backslash as escape character.
Additionally escaped backslashes are not removed by regexify any more.

Review checklist

• All checks have passed
• Changes are approved by maintainer

[pimjansen]

Needs rebase

[krsriq]

@pimjansen - done!

[pimjansen]

Phpcs is not green yet

[krsriq]

Too quick with these style changes 😁