[Feature request] independent setting support for external disk cache

### Basic Information

* Macbook pro 2018 15'

* macOS 13.0 beta 7

* Monitor: Studio Display

Since I bought this brand new 5k monitor, I prefer to load high-resolution videos in cache. It's insane. Absolutly wondful app of its kind.

I have limited storage of my mac. I would only give 5GB for internal video cache. However the 4k resources are huge. I have a thunderbolt external storage wth tons of space for more videos. The problem is:

1) Setting the cache path to the external folder with 100GB limitation:

When I unplug the hard drive device, the setting changed to default interal path. but the 100GB limitation also works.

2) Setting small storage limitation (like 5GB):

When I plug the external hard drive device, the most videos will be removed since the limitation setting.

I would prefer an independt setting for two cache paths:

1) when i set external path and plug external device, they work.

2) when i set external path and unplug external device, the internal settings and cached videos work.

Search the Swift code for cache path and cache size settings, then trace how those settings behave when an external volume is unavailable. Reproduce the internal and external cache scenarios described in the issue. Done means the two cache locations retain independent limits and cached videos remain usable when the external disk is unplugged.

Written by the indexing model from the issue text.