docs: Add documentation for EVE memory settings.

This commit introduces a detailed documentation file that explains the
memory settings for EVE OS. It covers the following topics:

- Overview of cgroups and their memory limits in EVE OS.
- Detailed explanation of soft and hard memory limits.
- Hierarchical structure of cgroups in EVE.
- Specific memory settings for EVE services and user applications.
- Recommendations for adjusting memory settings.
- Explanation of VMM overhead and how to override it.
- Handling of Out-Of-Memory (OOM) situations.

The documentation aims to provide clear guidelines for configuring
memory settings to optimize the performance and stability of EVE OS.

Signed-off-by: Nikolay Martyanov <[email protected]>