Runtime: ImmutableDictionary<K, V> should include key when throwing KeyNotFoundException

[terrajobst]

This looks like a regression because we merged a fix for that. Dictionary<K, V> still works as expected though.

Repro

Target .NET Core 3.1 and use the in-box version of immutable collections.

```C#
try
{
var d = ImmutableDictionary.Create();
Console.WriteLine(d["Immo"]);
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}

### Expected output

The given key 'Immo' was not present in the dictionary.

### Actual output

The given key was not present in the dictionary.
```

[msftbot[bot]]

Tagging @eiriktsarpalis as an area owner

[stephentoub]

This looks like a regression because we merged a fix for that. Dictionary still works as expected though.

That fix was about a duplicate key rather than about a non-existent key. The latter is just throwing a KeyNotFoundException, with the default message for that exception type:
https://github.com/akoeplinger/corefx/blob/25b88a4034e05ff189b9ea7b187dfcdb7286fc47/src/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableDictionary%602.cs#L258

[terrajobst]

Gotcha. I assume this means you've got no concerns with fixing this too though?

[stephentoub]

No concerns (other than the standard ones about exposing info, which we generally don't believe outweighs the benefits). cc: @danmosemsft who also cares a lot about this kind of thing.

[stephentoub]

(that said, it'd be nice to audit all such errors as part of the fix, rather than doing it piecemeal one exception at a time)

[danmosemsft]

This seems to be the only place we throw KNFE without a key. Aside from 3 in JsonElement.cs which I can't speak to.

Since the adding-duplicate case was mentioned, there may be some unrelated cleanup that could be done there: some collections that could use the more informational forms.

  <data name="Argument_AddingDuplicate" xml:space="preserve">
    <value>An item with the same key has already been added.</value>
  </data>
  <data name="Argument_AddingDuplicate__" xml:space="preserve">
    <value>Item has already been added. Key in dictionary: '{0}'  Key being added: '{1}'</value>
  </data>
  <data name="Argument_AddingDuplicateWithKey" xml:space="preserve">
    <value>An item with the same key has already been added. Key: {0}</value>
  </data>

  <data name="Argument_AddingDuplicate_OldAndNewKeys" xml:space="preserve">
    <value>Item has already been added. Key in dictionary: '{0}'  Key being added: '{1}'</value>
  </data>

[danmosemsft]

Re exposing info, it would be nice to consistently use quotes around replacement markers, so that "obfuscate between quotes before writing to log" is a potentially viable strategy. This one violates that: <value>An item with the same key has already been added. Key: {0}</value>