GODT-1667: bridge-gui spawns bridge process. [skip-ci]

Other: renaming of bridge-gui.
WIP: locate bridge exe.
WIP: bridge process launch.
WIP: cleaner closure of bridge.
WIP: grpcClient connection retries.
WIP: clean exit when bridge process is killed.

Fixed issues from MR review. [skip-ci].

WIP: Fixed gRPC case in CMakelists.txt [skip-ci]

It caused issues on Debian.

WIP: update gRPC/protobuf and tweaked CMakeLists.txt. [skip-ci]

WIP: Fixed a bug where splash screen could not be dismissed. [skip-ci]

internal/frontend/bridge-gui/qml/Proton/Dialog.qml

@@ -0,0 +1,80 @@
+// Copyright (c) 2022 Proton AG
+//
+// This file is part of Proton Mail Bridge.
+//
+// Proton Mail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Proton Mail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Proton Mail Bridge. If not, see <https://www.gnu.org/licenses/>.
+
+import QtQml 2.12
+import QtQuick 2.12
+import QtQuick.Templates 2.12 as T
+import QtQuick.Controls 2.12
+import QtQuick.Controls.impl 2.12
+
+T.Dialog {
+    id: root
+    property ColorScheme colorScheme
+
+    Component.onCompleted: {
+        if (!ApplicationWindow.window) {
+            return
+        }
+
+        if (ApplicationWindow.window.popups === undefined) {
+            return
+        }
+
+        var obj = this
+        ApplicationWindow.window.popups.append( { obj } )
+    }
+
+    readonly property int popupType: ApplicationWindow.PopupType.Dialog
+
+    property bool shouldShow: false
+    readonly property var occurred: shouldShow ? new Date() : undefined
+    function open() {
+        root.shouldShow = true
+    }
+
+    function close() {
+        root.shouldShow = false
+    }
+
+    anchors.centerIn: Overlay.overlay
+
+    implicitWidth: Math.max(implicitBackgroundWidth + leftInset + rightInset,
+    contentWidth + leftPadding + rightPadding,
+    implicitHeaderWidth,
+    implicitFooterWidth)
+    implicitHeight: Math.max(implicitBackgroundHeight + topInset + bottomInset,
+    contentHeight + topPadding + bottomPadding
+    + (implicitHeaderHeight > 0 ? implicitHeaderHeight + spacing : 0)
+    + (implicitFooterHeight > 0 ? implicitFooterHeight + spacing : 0))
+
+    padding: 24
+
+    background: Rectangle {
+        color: root.colorScheme.background_norm
+        radius: Style.dialog_radius
+    }
+
+    // TODO: Add DropShadow here
+
+    T.Overlay.modal: Rectangle {
+        color: root.colorScheme.backdrop_norm
+    }
+
+    T.Overlay.modeless: Rectangle {
+        color: "transparent"
+    }
+}