[12.x] Improve consistency and clarity in Filesystem Directories

[AhmedAlaa4611]

Description

This PR updates the Directories section of the Filesystem docs to improve consistency, tone, and clarity. Specifically:

• Simplifies wording (e.g., all of the files → all files, all the directories → all directories) for consistency.
• Uses a parallel sentence structure (e.g., within a given directory and all of its subdirectories → within a given directory including subdirectories) to enhance consistency and readability.

These changes do not affect the meaning or technical accuracy of the content.

[AhmedAlaa4611]

After this change, the phrasing used to describe file-related methods and directory-related methods will be structurally identical, making the documentation easier to read and compare.