Use filename in cache key to prevent collisions under rename

[SJrX]

Fixes #2241 #1678

Description

Issues #2241 #1678 both point to cases where renames can point to incorrect images being used with caching. This commit adds the path of the file (relative to the build context to the hash).

A different approach would be to change the underlying function in CacheHasher to include the name (and maybe file size), this was avoided for two reasons:

1. It was unclear whether this would change or break the computed digests outside the context of caching.
2. The CacheHasher does not know the prefix to strip in the filename to compute the hash.

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• [x] Includes unit tests
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Reviewer Notes

• [ ] The code flow looks good.
• [ ] Unit tests and or integration tests added.

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