Refactor Zoekt search mode

What does this MR do and why?

Add a new class Search::Gitlab::Zoekt::Query which is responsible for modifying the search query entered by the user. The public method exact_search_query will wrap the user-inputted query with the double quotes. If there is any syntax filter then it will not include these filters in the wrapped query. Currently, we are supporting these syntax filters: case, f, file, lang

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Before	After

How to set up and validate locally

• Setup Zoekt for a namespace
• Make sure the checkbox Enable Zoekt code search under User Preferences is checked
• Enable the feature flag zoekt_exact_search

Feature.enable(:zoekt_exact_search)

• Perform a code search in the chosen namespace without any syntax filter.
• Open the zkt section in the performance bar. Ensure the searched term is wrapped with a double quote
• Perform a code search in the chosen namespace with a syntax filter. For eg: test case:no.
• Open the zkt section in the performance bar. Ensure the filter is not wrapped with the double quotes but only test is wrapped.
• Perform a code search in the chosen namespace with multiple syntax filters. For eg: test case:no f:test/spec/constructor_spec.js.
• Open the zkt section in the performance bar. Ensure the filter is not wrapped with the double quotes but only test is wrapped.

Related to #438213 (closed)