fastboot: Introduce connect / disconnect for network-connected devices

Use introduced FileLock and network-connected devices storage entities
to introduce fastboot connect / disconnect commands

Test: everything works like discussed here go/fastboot-connect-disconnect on windows/linux
Bug: 267507450
Bug: 267506875
Change-Id: I2d6495ad567a3ddadd471a89b82d78c8c36a3d52
Signed-off-by: Dmitrii Merkurev <dimorinny@google.com>