Add support for "shallow" ETags

[tvallin]

Environment Details

• Helidon Version: 4.x
• Helidon MP
• JDK version: 21
• OS: n/a
• Docker version (if applicable): n/a

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Problem Description

Create a Etag Header filter that caches the content written to the response and calculate Hash from it. On the next request it does the same and compares the computed value against If-None-Match header value and return 304 status code if they match