fix LIKE ESCAPE with backslash

[AaryavGangrade]

Thank you for the time you are putting into AlaSQL!

Fixes #1978.

Backslash was not working correctly as the ESCAPE character in LIKE expressions because the escape value could reach utils.like() as a two-character backslash representation.

This change normalizes that representation to a single backslash before processing the LIKE pattern.

Tests

• Added regression tests in test/test1978.js
• Verified backslash escaping with alasql.utils.like()
• Verified the SQL LIKE ... ESCAPE '\\' reproduction from the issue
• Existing LIKE tests in test/test366.js and test/test369.js pass

[mathiasrw]

@AaryavGangrade Thank you for this.

Can you see if you can find a more generic solution? This only accounts for \\ but what about \\\ or \\\\?

[AaryavGangrade]

yes @mathiasrw Ill look into that

[AaryavGangrade]

Hi @mathiasrw I have pushed the code to make it generic
On a side note I noticed that patternCache keys only on pattern without the escape character if you want I can fix it in a separate PR.

[AaryavGangrade]

@mathiasrw Actually I am new to this open source contribution
Is the commit successful? And what are the next steps