[$] Finishing the conversion to the "new" mount API

Eric Sandeen led a filesystem-track session at the2024 Linux Storage,Filesystem, Memory Management, and BPF Summit on completing theconversion of the existing kernel filesystems to use the mount API that was added for the 5.2 kernel in 2019. That API isinvariably called the "new" API, which it is when compared to thevenerable mount()system call, but it has been available for five years or so at this pointwithout really pushing its predecessor aside. Sandeen wanted to discussthe status of the conversion process and some other questions surroundingthe new API.