chore: remove anyhow from task cache (#6013)
### Description
In general we're trying to move away from anyhow. On a more operational
level since a cache miss is reported as an error, keeping our own error
variant where it's easy to check if it is a `CacheError::CacheMiss`
without downcasting is preferable.
### Testing Instructions
`cargo check`
Closes TURBO-1351
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Co-authored-by: Chris Olszewski <Chris Olszewski>
