dotnet-dump command line UX for displaying help could be improved

### Description

The UX around retrieving the command line help isn't documented and could be improved.

### Examples using (version '3.1.141901')

1. Running `dotnet-dump` doesn't give any indication that help can be retrieved for the subcommands.

``` console
# dotnet-dump
Required command was not provided.

Usage:
dotnet-dump [options] [command]

Options:
--version Display version information

Commands:
collect Capture dumps from a process
analyze Starts an interactive shell with debugging commands to explore a dump
ps Lists the dotnet processes that dumps can be collected

# dotnet-dump -h
Usage:
dotnet-dump [options] [command]

Options:
--version Display version information

Commands:
collect Capture dumps from a process
analyze Starts an interactive shell with debugging commands to explore a dump
ps Lists the dotnet processes that dumps can be collected
```

I would expect `-h|--help` to be listed as a supported option. More importantly I would expect there would be an indication of how to retrieve additional help for each of the commands. The options parser doesn't appear to support this format -`dotnet-docker -h ps` so I would suggest displaying a message for how to retrieve the command help such as `Run 'dotnet-dump [Command] --help' for more information on a command.`

2. Top level help documentation for analyze is incomplete.

``` console
# dotnet-dump -h
Usage:
dotnet-dump [options] [command]

Options:
--version Display version information

Commands:
collect Capture dumps from a process
analyze Starts an interactive shell with debugging commands to explore a dump
ps Lists the dotnet processes that dumps can be collected
```

Showing `` here for the `analyze` command is strange to me because it feels incomplete because there are other supports args. This is inconsistent with the .NET cli. My suggestion is to just list the commands in the top level help. Require the users to display the `analyze` help and show them the full cmd syntax.