tiup-cluster: auto-detect architecture

[kolbe]

Feature Request

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

Why do we require administrators to manually specify the architecture for each host in the cluster definition?

Describe the feature you'd like:

We should auto-detect the architecture by default.

If an explicit architecture is given, we should use that architecture instead of auto-detecting (in case there's some reason to want the OS to emulate/translate execution).

Why the featue is needed:

It is much easier for TiUP to execute uname -m or the equivalent after connecting to each host than for the administrator to have to manually configure the architecture.

Describe alternatives you've considered:

Teachability, Documentation, Adoption, Migration Strategy:

[9547]

Technically, this is a good feature request, but currently, we need to download the binary packages first, especially in the offline scenario, if the CPU architecture is not specified, then we need to download all the CPU arch packages, maybe huge and slow? On the other hand, I'm not sure whether or not with mixed deployments of different CPUs are currently supported(not related to this issue).

[kolbe]

TiUP downloads all kinds of stuff "automatically" when some local package is missing, why not just do that at the time that it connects to each node during the cluster deploy phase?

[9547]

/assign