feat(http): Implement soft and hard TTL for all cache providers

[zharinov]

Changes

• Move TTL logic to abstract provider
• For repository cache, set soft ttl to zero, and hart TTL to 365 days
• For package cache, nothing changes
• Don't require cache to have at least one of etag or lastModified, now they're optional (useful for future memory cache implementation)

Context

Documentation (please check one with an [x])

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How I've tested my work (please select one)

I have verified these changes via:

• Code inspection only, or
• Newly added/modified unit tests, or
• No unit tests but ran on a real repository, or
• Both unit tests + ran on a real repository