These changes add a new flag to the CLI, `--profiling`, that enables
CPU and heap profiling as well as execution tracing of the CLI itself.
The argument to this flag serves as a prefix for the profile outputs;
the CPU and heap profiles and execution trace are written to
`[filename].[pid].{cpu,mem,trace}`, respectively.
These changes also fix an issue with `cmdutil.RunFunc` wherein any error
would prevent the command's post-run hooks from executing.
