feat(system_monitor): add diagnostic feature for monitoring swap usage

[ito-san]

Description

In the cargo project, it is said that "swap occurring indicates a problem," so the request is to trigger a warning when swap happens.
When the threshold is exceeded, a warning or error will be triggered.

Related links

Parent Issue:

• TIER IV JIRA internal link

How was this PR tested?

1. Enable and configure a 1GB swap file with high swappiness.

   sudo fallocate -l 1G /swapfile
   sudo chmod 600 /swapfile
   sudo mkswap /swapfile
   sudo swapon /swapfile
   sudo sysctl vm.swappiness=100

2. Launch system_monitor. Verify that no error messages related to 'mem_monitor after launching.
   

3. Use a tool like stress to apply load on the memory and make the system use swap.

   ex.) stress --vm 1 --vm-bytes 11900M --timeout 60s

4. Verify that warning is triggered when the threshold for warning is exceeded.
   

5. Verify that error is triggered when the threshold for error is exceeded.
   

Notes for reviewers

None.

Interface changes

None.

Effects on system behavior

None.

[TetsuKawa]

LGTM!

My old branches have been put to rest. Thanks.