HTTP Client Chunked Support

[stephenberry]

Add chunked transfer-encoding support to HTTP client

Problem

The synchronous and asynchronous request paths in glz::http_client only read response bodies based on the Content-Length header. When a server uses Transfer-Encoding: chunked (common with proxies like Cloudflare, streaming APIs, and many HTTP/1.1 servers), the Content-Length header is absent. The client returns a 200 status with headers parsed correctly but an empty response_body.

Reported in #2410.

Changes

include/glaze/net/http_client.hpp

Synchronous path (perform_sync_request):

• Detect Transfer-Encoding: chunked header during response parsing
• Implement a chunked decoding loop: read hex chunk size, read chunk data, append to body, repeat until the terminal 0 chunk
• Properly skip optional trailer headers after the terminal chunk (RFC 7230 §4.1)
• Handle chunk extensions (;key=value) by ignoring them
• Return protocol_error on malformed chunk sizes

Asynchronous path (parse_and_read_body):

• Same header detection for chunked encoding
• New async_read_chunked_body / async_read_chunk_data methods implementing chunked decoding via recursive async reads
• New async_consume_trailers method to skip trailer headers before building the response and returning the connection to the pool

Portability fix:

• Replace bare strncasecmp (POSIX-only) with glz::strncasecmp in the sync path header parsing for Content-Length, Transfer-Encoding, and Connection headers

Tests (tests/networking_tests/http_chunked_test/)

New test suite with 43 tests covering:

• Sync path (14 tests): single chunk, multi-chunk, empty body, large body (100KB), binary data with null bytes, custom headers, many tiny chunks, varying chunk sizes, POST echo, sequential requests, interleaved chunked/content-length, concurrent requests
• Async path (10 tests): mirrors of key sync tests via get_async/post_async futures, concurrent async requests to mixed endpoints, callback-based async with large body
• Streaming path (4 tests): stream_request_v2 with on_data callbacks for single/multi/large/empty chunked responses
• Raw socket edge cases (15 tests): hand-crafted HTTP responses testing basic chunked decoding, single-byte chunks, chunk extensions, uppercase/lowercase hex, empty body, large hex sizes, case-insensitive headers, Connection: close, connection reuse after chunked response, malformed chunk sizes, empty chunk size lines, server disconnect mid-chunk, trailer headers after terminal chunk, trailer + connection reuse, leading zeros in chunk size, multiple transfer encodings (gzip, chunked)

Documentation (docs/networking/max-response-body-size.md)

Proposal for a future configurable maximum response body size to guard against unbounded memory growth from malicious servers. This applies equally to content-length and chunked paths and is tracked separately from this change.

[packit-as-a-service]

One of the tests failed for 14f9ff1. @admin check logs None, packit dashboard https://dashboard.packit.dev/jobs/srpm/575978 and external service dashboard https://copr.fedorainfracloud.org/coprs/build/10274458/