fix: parse escape sequences in regex replacement text

[4RH1T3CT0R7]

Motivation

Fixes #2803

When using global search and replace with regex mode enabled, escape sequences like \n in the replacement text are inserted as literal characters instead of
being interpreted as actual newlines. For example, replacing \n\n with \n produces #define hello\n instead of an actual newline character.

Change description

• Added parseReplaceString() function that converts escape sequences (\n, \t, \r, \) to their actual character representations
• Created custom SearchInWorkspaceResultTreeWidget that overrides replaceResult() to parse escape sequences when regex mode is enabled
• Added rebinding in the frontend module to use the custom widget
• Added unit tests for the escape sequence parser

Other information

• Escape sequences are only parsed when regex mode (useRegExp) is enabled
• In non-regex mode, \n remains literal as expected
• Related upstream issue: [search-in-workspace] Support regular expression substitution eclipse-theia/theia#6420

Reviewer checklist

• PR addresses a single concern.
• The PR has no duplicates (please search among the https://github.com/arduino/arduino-ide/pulls before creating one)
• PR title and description are properly filled.
• Docs have been added / updated (for bug fixes / features)

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