Make codebase compatible with Boost 1.85 deprecation removals

[mcserep]

Cherry-picked from #637.

[Copilot]

Pull Request Overview

This PR updates the codebase to address Boost 1.85 deprecation removals. It replaces legacy Boost filesystem functions with their updated equivalents and standardizes extension extraction using fs::path().extension(), ensuring compatibility for dynamic library identification and file type checks.

• Updated Boost filesystem calls from is_regular and extension() to their updated counterparts.
• Ensured proper conversion (using .string() where needed) in cases of file extension comparisons.
• Applied consistent changes across plugins, parsers, and services to support Boost 1.85.

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
webserver/include/webserver/pluginhandler.h	Revised extension extraction via fs::path() for dynamic libraries.
plugins/search/parser/src/searchparser.cpp	Updated is_regular_file() for file regularity checks.
plugins/git/service/src/gitservice.cpp	Replaced deprecated is_regular with is_regular_file for repo files.
plugins/git/parser/src/gitparser.cpp	Updated filesystem regular file check for repository handling.
plugins/dummy/parser/src/dummyparser.cpp	Adopted fs::path().extension() using auto for extension extraction.
plugins/cpp/service/src/filediagram.cpp	Converted extension extraction to use fs::path() and .string().
plugins/cpp/parser/src/cppparser.cpp	Updated extension extraction and integrated similar conversion logic.
parser/src/pluginhandler.cpp	Standardized dynamic library extension extraction via fs::path().