wiki: document gomote for first time users

[eliasnaur]

Thanks for this. If there's one thing that could make the wiki significantly clearer it would be a paragraph about directory structure and the "gomote machine model". It took me a bunch of try-and-error runs to find out. Much of it may be "obvious" in retrospect, but it helps spelling it out right away, especially for first-time gomote users. This would provide newcomers a clearer model of how the gomote looks like from a client's perspective.

Some of the things that would be nice if they were spelled out:

• each instance of a gomote has its own working directory, accessible via $WORKDIR
• gomote push does essentially an rsync of the $GOROOT directory into the remote $WORKDIR; i.e., after a gomote push, the local $GOROOT appears as go directory on the gomote (I had to find this out by doing repeated gomote ls commands)
• when issuing gomote run commands, one needs to specify the full path for commands and files, e.g. go/bin/go tool compile go/src/mypkg/x.go - there appears no notion of a cwd, or perhaps I missed it
• to change individual uploaded files, make the changes locally and use gomote push $MOTE and it will only upload the changes (this was not obvious to me at first, especially because there's also a gomote put command to push single files. I thought I was supposed to use that one for smaller changes)
• I didn't figure out to how to use gomote put to get a file into a specific directory on the gomote instance (I still don't know how to do it, but I resorted to just using gomote push all the time.)
• explain that the gomote self-destructs after 30min of non-use
• I'm unclear on the -system flag

Originally posted by @griesemer in #31091 (comment)

[mknyszek]

I updated the wiki and I think I hit your main points: https://github.com/golang/go/wiki/Gomote.

Closing for now. Feel free to reopen.