perf: use textproto.TrimString for HTTP header parsing to improve performance

[1911860538]

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Replaced strings.TrimSpace with textproto.TrimString in HTTP header parsing functions to improve performance and better align with HTTP spec.
textproto.TrimString, which is widely used in net/http, trims only ASCII whitespace—making it both sufficient and more efficient for HTTP headers like X-Forwarded-For and Accept.