Switched from grpc to @grpc/grpc-js.

This change is required to be able to support ARM arch
in the future.

 - Fixed the download links for armv7l Linux.
 - Checked in the generated code. [grpc/grpc-node#1497]
 - Made the code generation a manual step.
 - Made the `grpc-tools` dependency optional.
 - From now on, the serial port regex is case-insensitive.

Signed-off-by: Akos Kitta <kittaakos@typefox.io>

arduino-ide-extension/scripts/download-cli.js

@@ -42,6 +42,7 @@
             case 'win32': return 'Windows_64bit.zip';
             case 'linux': {
                 switch (arch) {
+                    case 'arm': return 'Linux_ARMv7.tar.gz';
                     case 'arm64': return 'Linux_ARM64.tar.gz';
                     case 'x64': return 'Linux_64bit.tar.gz';
                     default: return undefined;