Ability to obtain flame graphs

Since [flame graph](https://github.com/brendangregg/flamegraph) supports [bpftrace](https://github.com/iovisor/bpftrace) I propose to create a new feature making users of kubectl-trace able to obtain flame graphs.

Not sure yet whether such feature should be implemented from a flag or from a new command.

We'll investigate further cc @fntlnz.

No file, test, or entry point is named. Start by reviewing how kubectl-trace currently exposes commands and flags, then examine the linked bpftrace and flame graph projects. Done means users can obtain flame graphs through a defined kubectl-trace interface.

Written by the indexing model from the issue text.