temp/modemmanager: upgrade to 1.18rc1 aka 1.17.900
As discussed with @Minecrell, since he is temporarily busy, I am opening a new MR to get MM 1.18rc1 (1.17.900) merged into edge for wider testing before the stable release. Tested in Poco F1 (SDM845). Kindly let me know if any changes are needed. The old MR !2228 (closed) we used for testing can be closed when we merge this.