feat: create a Rust sample for normalize HTTP header plugin.

[walves-cit]

This plugin is a normalize request header showcase.

Technically, this is performed by creating a new HTTP header client-device-type to shard requests based on device according to the existence of the HTTP Client Hints header or the User-Agent value set.

This examples contains only a Rust version.

[snippet-bot]

Here is the summary of changes.

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• plugins/samples/normalize_header/plugin.rs:15, tag serviceextensions_plugin_normalize_header

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