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/MenuItem.qml

@@ -0,0 +1,72 @@
+// 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 QtQuick 2.12
+import QtQuick.Controls 2.12
+import QtQuick.Controls.impl 2.12
+import QtQuick.Templates 2.12 as T
+import "."
+
+T.MenuItem {
+    id: control
+
+    property ColorScheme colorScheme
+
+    implicitWidth: Math.max(implicitBackgroundWidth + leftInset + rightInset,
+    implicitContentWidth + leftPadding + rightPadding)
+    implicitHeight: Math.max(implicitBackgroundHeight + topInset + bottomInset,
+    implicitContentHeight + topPadding + bottomPadding,
+    implicitIndicatorHeight + topPadding + bottomPadding)
+
+    padding: 6
+    spacing: 6
+
+    icon.width: 24
+    icon.height: 24
+    icon.color: control.enabled ? control.colorScheme.text_norm : control.colorScheme.text_disabled
+
+    font.family: Style.font_family
+    font.weight: Style.fontWeight_400
+    font.pixelSize: Style.body_font_size
+    font.letterSpacing: Style.body_letter_spacing
+
+    contentItem: IconLabel {
+        id: iconLabel
+        readonly property real arrowPadding: control.subMenu && control.arrow ? control.arrow.width + control.spacing : 0
+        readonly property real indicatorPadding: control.checkable && control.indicator ? control.indicator.width + control.spacing : 0
+        leftPadding: !control.mirrored ? indicatorPadding : arrowPadding
+        rightPadding: control.mirrored ? indicatorPadding : arrowPadding
+
+        spacing: control.spacing
+        mirrored: control.mirrored
+        display: control.display
+        alignment: Qt.AlignLeft
+
+        icon: control.icon
+        text: control.text
+        font: control.font
+
+        color: control.enabled ? control.colorScheme.text_norm : control.colorScheme.text_disabled
+    }
+
+    background: Rectangle {
+        implicitWidth: 164
+        implicitHeight: 36
+        radius: Style.button_radius
+        color: control.down ? control.colorScheme.interaction_default_active : control.highlighted ? control.colorScheme.interaction_default_hover : control.colorScheme.interaction_default
+    }
+}