[Improvement] Better handling of quoted phrases in synonyms

[Fix] Synonyms not working with non-ASCII strings

[Fix] Max nesting function when synonyms are applied

[Fix] Synonyms are not case-insensitive

[Fix] Synonyms affecting the stemming functionality

[Fix] Metrics related click tracking error in multisite environment

[Fix] Merging words during HTML content tokenization if is used in the content

[Fix] Hiding SearchWP admin menu via the hook leaves a link to it in the admin bar menu

[Fix] MySQL error if engine sources have no attributes

[Fix] Error if 's' parameter in the request is not a string

[Fix] Warning if a custom field is added to the Users in the engine settings

[Fix] Return type compatibility notice in PHP 8.1 for jsonSerialize() method

- **[Fix]** Edited document content is not preserved

- **[Fix]** Broken URLs for the redirects to the legacy admin settings

- **[Fix]** Class prefixing error in smalot/pdfparser lib

- **[Fix]** PHP7 static code analyzer error in symfony/polyfill-mbstring lib

- **[Change]** Plugin settings moved to the top-level menu

- **[Fix]** Undefined function error during the 'index' CLI command execution

- **[Fix]** Merging words in some cases during HTML content tokenization

- **[Fix]** Synonym application too broad in some cases

- **[Fix]** Document content reindexing in some cases

- **[Fix]** Missing method reference in Comment source

- **[Fix]** Forced phrase search returns no results if the search string doesn't contain non-phrase tokens

- **[Improvement]** Search string normalization

- **[Improvement]** String highlight application when synonyms are applied

- **[Improvement]** Handling of double quotes in synonym logic in some cases