Integrate signal-cli for primary device support

[Gredin67]

v5 deprecated linking mautrix-signal as a primary device, we could add signal-cli to re-enable it:
https://github.com/AsamK/signal-cli

[Gredin67]

There is a debian package available
https://packaging.gitlab.io/signal-cli/installation/standalone/index.html
See also instructions for backup
https://packaging.gitlab.io/signal-cli/backup/index.html

[Gredin67]

On some old laptop I get : The current machine does not support all of the following CPU features that are required by the image: [CX8, CMOV, FXSR, MMX, SSE, SSE2, SSE3, SSSE3, SSE4_1, SSE4_2, POPCNT]
But a VPS it is working fine :D