Retain file handle for disk fill experiment

[xcaspar]

Issue Description

Type: feature request

Describe what happened (or what feature you want)

The blade will exit after creating a large file in disk fill experiment currently, although it simulates disk occupancy, but it cannot realistically simulate the continuous writing of log files, it is difficult to find which files occupy the disk, so we need to keep the written file handle.

Describe what you expected to happen

Add --retain-handle flag to retain temp file handle.

How to reproduce it (as minimally and precisely as possible)

blade c disk fill --percent 60 --retain-handle

Tell us your environment

Anything else we need to know?