Cache expected missing manifest read (#89908)
## What
Found a bug. When a manifest is expectedly missing (`handleMissing`
option) it would not hit the caching for manifest loading. Causing a
readFileSync that fails every time it's called and doesn't get cached.
## How
This PR resolves the issue by moving the handleMissing to the function
that handles the manifest caching. Making sure we cache the result even
when the file is not available.
