Support file uploads and the device details page for Elegoo Centauri Carbon 2 (#13212)

* Support file uploads and the device details page for CC2 printers.

* Resolved build issues for Linux and macOS.

* 1. Added `ElegooPrinterWebViewHandler` to handle WebUI messages for Elegoo printers. Other printers will keep the current behavior.
2. Added a static `get_print_host_webui` method in `PrintHost` to retrieve the printer WebUI URL.

* Improved timeout handling for CC2 file upload and SN info APIs.

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Co-authored-by: SoftFever <softfeverever@gmail.com>

src/slic3r/Utils/Http.hpp

@@ -109,6 +109,8 @@ public:
 	Http& set_range(const std::string& range);
 	// Sets a HTTP header field.
 	Http& header(std::string name, const std::string &value);
+	// Clears all custom headers and restores default implicit headers.
+	Http& headers_reset();
 	// Removes a header field.
 	Http& remove_header(std::string name);
 	// Authorization by HTTP digest, based on RFC2617.