Thumbnail Formats Option Ported from PrusaSlicer and add BIQU/BTT format (#2405)

* Add needed src files and update CMake files

* Implementation of GCodeThumbnailsFormat for PNG, JPG, and QOI complete

* Implement BIQU (Big Tree Tech) Thumbnail Format

* have GCodeProcessor.post_process pass through original line end characters

* fix biqu thumbnail output
use \r\n for new lines in the biqu thumbnail portion. the firmware requires these end characters to function properly.
update names of variables and add comments to be more descriptive
replace modified Qt pixel algorithm with much simpler algorithm from BTT TFT firmware

* rename BiQU to BTT_TFT for better clarity

* remove underscore from GUI option

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Co-authored-by: SoftFever <103989404+SoftFever@users.noreply.github.com>

src/libslic3r/GCode/GCodeProcessor.cpp

@@ -668,7 +668,10 @@ void GCodeProcessor::TimeProcessor::post_process(const std::string& filename, st
                 if (eol) {
                     ++line_id;
 
-                    gcode_line += "\n";
+                    // determine the end of line character and pass to output
+                    gcode_line += *it_end;
+                    if(*it_end == '\r' && *(++ it_end) == '\n')
+                        gcode_line += '\n';
                     // replace placeholder lines
                     auto [processed, lines_added_count] = process_placeholders(gcode_line);
                     if (processed && lines_added_count > 0)