[llvm-profdata] Allow omission of -o for --text output

This makes it more convenient to get a text format profile.

Add an error for printing non-text format output to a terminal for instrumentation profile.
(It cannot be portably tested. For sample profile, raw_fd_ostream is hidden deeply so it's inconvenient to add a diagnostic.)

Reviewed By: davidxl

Differential Revision: https://reviews.llvm.org/D104600