headers: add length argument to Curl_headers_push()

[bagder]

• the length is already known by parent functions
• avoids strlen() calls
• avoids strchr() calls for trimming off newline characters

[bagder]

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[Copilot]

Pull request overview

This PR optimizes the Curl_headers_push() function by adding a length parameter to eliminate redundant string operations. The length is already known by calling functions, so passing it directly avoids expensive strlen() calls and strchr() searches for line ending detection.

Key changes:

• Added size_t hlen parameter to Curl_headers_push() function signature
• Replaced strchr()-based newline detection with direct index-based trimming
• Updated call sites to pass the length value (from curl_msnprintf return value and existing buffer length)

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
lib/headers.h	Updated function declaration to include the new hlen parameter
lib/headers.c	Modified implementation to accept length parameter and replaced newline detection logic with more efficient character-by-character trimming from the end
lib/http2.c	Updated call site to capture curl_msnprintf return value and pass it as the length parameter

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