Support setting CPUAffinity through TiUP

[sticnarf]

Feature Request

Is your feature request related to a problem? Please describe:

Sometimes I have a server with many cores, so I want to deploy multiple TiDB or TiKV nodes on one server. And I hope different nodes on the same server don't interfere with each other.

It's still a luxury to deploy only one process on one NUMA node. But TiUP does not provide a way to isolate processes in a more fine-grained mode.

Describe the feature you'd like:

Systemd provides CPUAffinity option. I hope TiUP cluster can integrate this feature to set CPU affinity through cluster configuration file.

Why the featue is needed:

Have described my scenario above :)

Describe alternatives you've considered:

Now I need to patch the systemd service manually.

Teachability, Documentation, Adoption, Migration Strategy:

Doc for CPUAffinity: https://www.freedesktop.org/software/systemd/man/systemd-system.conf.html