Consider adding more fields to the "Copy description" from marker command

I frequently use the "Copy description" command from the context menu to grab relevant marker output, e.g.

However what is copied to the clipboard does not include the "Start" field with the Start time.
For example, this is what is copied for the given marker:

```LogMessages — (nsHttp) MaybeSpeculativeConnectWithHTTPSRR for ci=.S........[tlsflags0x00000000]theme-crave-demo.myshopify.com:443^partitionKey=%28https%2Ctheme-crave-demo.myshopify.com%29```

I would be very useful for me if the "Start" field was also included, i.e.
```1.332s LogMessages — (nsHttp) MaybeSpeculativeConnectWithHTTPSRR for ci=.S........[tlsflags0x00000000]theme-crave-demo.myshopify.com:443^partitionKey=%28https%2Ctheme-crave-demo.myshopify.com%29```

This is very useful when describing profiles in bugs etc.

example profile: https://share.firefox.dev/4n9Ku3q

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-916)