funclatency to accept multiple events

eg, to support:

```
# funclatency vfs_read vfs_write
```

In that case, we can do:

```
# funclatency 'vfs_(read|write)'
```

But other cases get trickier.

I'm also wondering if the -F logic should be flipped. So that if you match multiple functions, then by default split them in the output, and only use -F to merge them if desired.

Start by locating the funclatency command implementation and its existing -F handling; no file or test is named in the issue. Reproduce the single-event behavior, then determine the intended semantics for multiple events and verify separate versus merged output with focused tests.

Written by the indexing model from the issue text.