Streamline usage of chmod() in FileSystem

Problem/Motivation

The FileSystem class has a chmod() method, which calls the PHP chmod() function.

However several of the other methods within the FileSystem class also call chmod() directly instead of using the internal function. There does not appear to be a reason for this practice. Using the chmod() method will add features such as logging of errors and other helpful elements which might be added down the line.

Steps to reproduce

N/A

Proposed resolution

Update all methods within the FileSystem class to call self::chmod() instead of calling chmod directly e.g. unlink(), mkdir(), rmdir()

Merge request link

Remaining tasks

User interface changes

None.

API changes

None.

Data model changes

None.

Release notes snippet