fastboot driver: add RunAndReadBuffer helper

Refactor UploadInner and add a new RunAndReadBuffer helper function
that handles the generic procedure of:

1. Sending a command
2. Receiving a DATA response with N bytes
3. Receiving another response

Test: pass
Bug: 173654501

Change-Id: I568bea127315e42d8a111c23602fc582e7bc935b