`brev create` searching has gaps; best practices for search + create are unclear

[brycelelbach]

Creating a brev node from the CLI involves two tasks:
1.) Finding an instance type. These have provider specific names that are not human friendly.
2.) Creating an instance of that type.

Today, to find an instance type, you can either:

• Find it manually (not recommended, and may change due to availability).
• Use brev search, which can be piped into brev create.
• Use brev create, which has some but not all of the options of brev create.
  • brev create has no "CPU" mode and can't search for CPU instances. See brev create should have two subcommands, brev create gpu and brev create cpu, mirroring brev search #376.
  • brev create doesn't have all of the flags of brev search gpu: it's missing --arch and --total-ram. See brev create and brev search flags for # of processors and amount of memory are confusing and inconsistent #373 and brev create and brev search flags for processor architecture are inconsistent #374.

Questions:

• Do both brev create and brev search go through the same codepath for doing searching?
• Is brev search | brev create the new best practice? If so we should say brev create is deprecated somewhere.