Manage toolchains

Enabled notifications for the download and installation of more than two toolchains at the same time.
Updated nRF Util binaries bundled with the extension, including nrfutil-device to v2.5.0.
Updated the Install Toolchain menu behavior so that toolchains that are being installed are now hidden.
Fixed the updating of the CPP tools integration when the toolchain changes.
Fixed an issue when updating the toolchain entry in the Welcome View.
Fixed an issue with executing the installation of nRF Command Line Tools on Linux.
Fixed a Windows-only issue with the device enumeration with nRF Util.
Fixed an issue with the GDB path resolution when the toolchain was manually installed.
Fixed a macOS-only issue with the binary architecture check when a toolchain tool does not exist.