ggml: Add initial WebGPU backend (#14521)

* Minimal setup of webgpu backend with dawn. Just prints out the adapter and segfaults

* Initialize webgpu device

* Making progress on setting up the backend

* Finish more boilerplate/utility functions

* Organize file and work on alloc buffer

* Add webgpu_context to prepare for actually running some shaders

* Work on memset and add shader loading

* Work on memset polyfill

* Implement set_tensor as webgpu WriteBuffer, remove host_buffer stubs since webgpu doesn't support it

* Implement get_tensor and buffer_clear

* Finish rest of setup

* Start work on compute graph

* Basic mat mul working

* Work on emscripten build

* Basic WebGPU backend instructions

* Use EMSCRIPTEN flag

* Work on passing ci, implement 4d tensor multiplication

* Pass thread safety test

* Implement permuting for mul_mat and cpy

* minor cleanups

* Address feedback

* Remove division by type size in cpy op

* Fix formatting and add github action workflows for vulkan and metal (m-series) webgpu backends

* Fix name

* Fix macos dawn prefix path

ggml/src/ggml-webgpu/wgsl-shaders/embed_wgsl.py

@@ -0,0 +1,35 @@
+import os
+import argparse
+
+
+def escape_triple_quotes(wgsl):
+    # Simple defense in case of embedded """
+    return wgsl.replace('"""', '\\"""')
+
+
+def to_cpp_string_literal(varname, content):
+    return f'const char* wgsl_{varname} = R"({content})";\n'
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--input', required=True)
+    parser.add_argument('--output', required=True)
+    args = parser.parse_args()
+
+    with open(args.output, 'w', encoding='utf-8') as out:
+        out.write("// Auto-generated shader embedding \n\n")
+        for fname in sorted(os.listdir(args.input)):
+            if not fname.endswith('.wgsl'):
+                continue
+            shader_path = os.path.join(args.input, fname)
+            varname = os.path.splitext(fname)[0]
+            with open(shader_path, 'r', encoding='utf-8') as f:
+                content = f.read()
+            content = escape_triple_quotes(content)
+            out.write(to_cpp_string_literal(varname, content))
+            out.write('\n')
+
+
+if __name__ == '__main__':
+    main()