dotnet-trace collect --help documentation should include option for launching a process

The `dotnet-trace collect --help` documentation does not mention the `--` option that can be used to launch a process so that you can trace startup as described [here](https://github.com/dotnet/diagnostics/blob/master/documentation/dotnet-trace-instructions.md#using-dotnet-trace-to-launch-a-child-process-and-trace-it-from-startup).

**Steps to Reproduce**
1. `dotnet-trace collect --help`

**Expected Results**
1. I expect the `--` option to be documented.
1. Possibly the summary text should be updated to indicate the command is capable of launching a process.

> Collects a diagnostic trace from a currently running process

**Actual Results**

``` console
> dotnet-trace collect --help
collect:
Collects a diagnostic trace from a currently running process

Usage:
dotnet-trace collect [options]

Options:
-p, --process-id The process id to collect the trace.
--buffersize Sets the size of the in-memory circular buffer in megabytes. Default 256 MB.
[default: 256]
-o, --output The output path for the collected trace data. If not specified it defaults to
'trace.nettrace'. [default: trace.nettrace]
--providers A list of EventPipe providers to be enabled. This is in the form
'Provider[,Provider]', where Provider is in the form:
'KnownProviderName[:Flags[:Level][:KeyValueArgs]]', and KeyValueArgs is in the
form: '[key1=value1][;key2=value2]'. These providers are in addition to any
providers implied by the --profile argument. If there is any discrepancy for a
particular provider, the configuration here takes precedence over the implicit
configuration from the profile. [default: ]
--profile A named pre-defined set of provider configurations that allows common tracing
scenarios to be specified succinctly. [default: ]
--format Sets the output format for the trace file. Default is NetTrace. [default:
NetTrace]
--duration When specified, will trace for the given timespan and then automatically stop
the trace. Provided in the form of dd:hh:mm:ss. [default: 00:00:00]
--clrevents List of CLR runtime events to emit. [default: ]
--clreventlevel Verbosity of CLR events to be emitted. [default: ]
-n, --name The name of the process to collect the trace.
-?, -h, --help Show help and usage information
```

**dotnet-trace --version**
5.0.152202+4d281c71a14e6226ab0bf0c98687db4a5c4217e3