Fix several oddities in Project Converter

This is not a complete list. Nor are all of the changes exhaustive.
- Measure final execution time in seconds instead of milliseconds.
- Use `vformat()` instead of unreadable string concatenation whenever necessary.
- Replaces every `&` used with booleans with `&&` because Visual Studio was really complaining about it.
- Adds punctuation to some comments, in accordance to codebase guidelines.
- Fixes some typos around the file (such as "parenthesis" being called "parenthess"), as well as attempt to change some sentences to be more English-correct.
- Reworded some comments and error messages entirely.

editor/project_converter_3_to_4.h

@@ -76,7 +76,7 @@ private:
 	Vector<String> check_for_files();
 
 	Vector<String> parse_arguments(const String &line);
-	int get_end_parenthess(const String &line) const;
+	int get_end_parenthesis(const String &line) const;
 	String connect_arguments(const Vector<String> &line, int from, int to = -1) const;
 	String get_starting_space(const String &line) const;
 	String get_object_of_execution(const String &line) const;