RunCommand tests: move in to a subdirectory

Dependencies

• [2] 2JJP7673 tests: move to t, allow `yath test` from root
• [3] T3HCJYPL Implement `yath`-test for the new Gitea plugin
• [4] 3AKZKWCR RunCommand: Test

Change contents

• file addition: RunCommand (d--r------)
  [2.2547]
• file move: runcommand.t (----------) → basic.t (----------)
  [0.1]

  [3.1230]