no-control-regex doesn't catch erros on escaped strings

[IllusionMH]

Bug Report

• tslint-microsoft-contrib version: 6.0.0
• TSLint version: 5.12.0
• TypeScript version: 3.1.1
• Running TSLint via: CLI

Difference in behavior during test mighration mentioned in comment

TypeScript code being linted

// should fail
new RegExp('something \x1f something else'); // creates regexp with special character in it (equivalent of /something � something else/)

new RegExp('something \\x1f something else'); // creates regexp with character match sequence in it (equivalent of /something \x1f something else/)

new RegExp('something \\\x1f something else'); // creates regexp that contains backslash followed by special character in it (equivalent of /something \� something else/)

// should pass
new RegExp('something \\\\x1f something else'); // creates regexp that correctly escaped backslash followed by characters x,1,f (equivalent of /something \\x1f something else/)

with tslint.json configuration:

{
    "rules": {
        "no-control-regex": true
    }
}

Actual behavior

Detected errors in strings with 1 and 3 \ characters (will also fail on 5 characters)
No errors in strings with 2 and 4 \ characters

Expected behavior

Should detect errors in strings with 1, 2, and 3 \ characters
No error in string with 4 \ characters

ESLint behavior (was prototype):

Will detect errors in strings with 1, 2, and 5 \ characters
Will detect no errors in strings with 3 and 4 \ characters.

Not sure why it passes on 3 \ characters, but it is up for discussion.

[JoshuaKGoldberg]

💀 It's time! 💀

TSLint is deprecated and no longer accepting pull requests other than security fixes. See #876. ☠️
We recommend you instead use typescript-eslint to lint your TypeScript code with ESLint. ✅

👋 It was a pleasure open sourcing with you!