HttpClient using libcurl, Unix Sockets for HTTP. HTTPS support (#770)

The main goal of this change is to eliminate the cpr back-end altogether and replace it with the curl implementation. I would expect to drop cpr as soon as we feel happy with the libcurl back-end. That would leave us with a direct dependency on libcurl only, and cpr can be eliminated as a dependency.

### HttpClient Backend Overhaul
- Implemented a new **libcurl-based HttpClient** backend (`httpclientcurl.cpp`, ~2000 lines)
  as an alternative to the cpr-based one
- Made HttpClient backend **configurable at runtime** via constructor arguments
  and `-httpclient=...` CLI option (for zen, zenserver, and tests)
- Extended HttpClient test suite to cover multipart/content-range scenarios

### Unix Domain Socket Support
- Added Unix domain socket support to **httpasio** (server side)
- Added Unix domain socket support to **HttpClient**
- Added Unix domain socket support to **HttpWsClient** (WebSocket client)
- Templatized `HttpServerConnectionT<SocketType>` and `WsAsioConnectionT<SocketType>`
  to handle TCP, Unix, and SSL sockets uniformly via `if constexpr` dispatch

### HTTPS Support
- Added **preliminary HTTPS support to httpasio** (for Mac/Linux via OpenSSL)
- Added **basic HTTPS support for http.sys** (Windows)
- Implemented HTTPS test for httpasio
- Split `InitializeServer` into smaller sub-functions for http.sys

### Other Notable Changes
- Improved **zenhttp-test stability** with dynamic port allocation
- Enhanced port retry logic in http.sys (handles ERROR_ACCESS_DENIED)
- Fatal signal/exception handlers for backtrace generation in tests
- Added `zen bench http` subcommand to exercise network + HTTP client/server communication stack

1 files changed, 0 insertions, 4 deletions

diff --git a/src/zenserver/storage/cache/httpstructuredcache.cpp b/src/zenserver/storage/cache/httpstructuredcache.cpp
index 06b8f6c27..bbdb03ba4 100644
--- a/src/zenserver/storage/cache/httpstructuredcache.cpp
+++ b/src/zenserver/storage/cache/httpstructuredcache.cpp
@@ -1892,8 +1892,6 @@ HttpStructuredCacheService::CollectStats()
 		{
 			Cbo << "upstream_ratio" << (HitCount > 0 ? (double(UpstreamHitCount) / double(HitCount)) : 0.0);
 			Cbo << "upstream_hits" << m_CacheStats.UpstreamHitCount;
-			Cbo << "upstream_ratio" << (HitCount > 0 ? (double(UpstreamHitCount) / double(HitCount)) : 0.0);
-			Cbo << "upstream_ratio" << (HitCount > 0 ? (double(UpstreamHitCount) / double(HitCount)) : 0.0);
 		}
 
 		Cbo << "cidhits" << ChunkHitCount << "cidmisses" << ChunkMissCount << "cidwrites" << ChunkWriteCount;
@@ -2025,8 +2023,6 @@ HttpStructuredCacheService::HandleStatsRequest(HttpServerRequest& Request)
 		{
 			Cbo << "upstream_ratio" << (HitCount > 0 ? (double(UpstreamHitCount) / double(HitCount)) : 0.0);
 			Cbo << "upstream_hits" << m_CacheStats.UpstreamHitCount;
-			Cbo << "upstream_ratio" << (HitCount > 0 ? (double(UpstreamHitCount) / double(HitCount)) : 0.0);
-			Cbo << "upstream_ratio" << (HitCount > 0 ? (double(UpstreamHitCount) / double(HitCount)) : 0.0);
 		}
 
 		Cbo << "cidhits" << ChunkHitCount << "cidmisses" << ChunkMissCount << "cidwrites" << ChunkWriteCount;