Add settings to ignore backticks in AI code completion

[JonasHelming]

fixed #14461

What it does

Adds a user setting to ignore backticks in LLM response for code completion. If a response starts with ```, it willremove opening and closing backticks and also remove any text after the closing backticks.

How to test

Use this prompt:
START_PROMPT

{{textUntilCurrentPosition}}[BLANK]{{textAfterCurrentPosition}}

Fill in the blank to complete the code block. Your response should include only the code to replace [BLANK], without surrounding backticks.
END_PROMPT
Or tweak the existing prompt by removing the order to only return the code.

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