fix: keep the snapshot list with relevant values (#382)

Description

• add a caching layer to avoid filesystem calls on each API request
• keep the state of FSManager on pool or configuration reloading

Related issue

#382 (closed)

Examples

Checklist

• MR description has been reviewed
• MR changes are functionally tested
• MR does NOT have text changes OR there are text changes and they have been reviewed
• MR does NOT have API/CLI changes OR there are API/CLI changes and they have been reviewed
• MR does NOT have UI changes OR there are UI changes and they have been reviewed

Closes #382 (closed)