Use shorter pipe names on iOS/macOS/Mac Catalyst

[kevinchalet]

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Describe the solution you'd like

Pipes are now disabled by default on iOS/macOS/Mac Catalyst but are still supported. Unfortunately, the default pipe name generated by OpenIddict combined to the prefix used by the .NET implementation is too long, which throws an exception on macOS:

The path '/var/folders/5j/jjxtct5j1gvg35z6sdh2fz0w0000gn/T/CoreFxPipe_OpenIddict.Client.SystemIntegration-_fF5_2tWzI54dfcnJYNS5rInXlVRpta1Stdk_yRKHQg\60a75d52-219c-4ba4-b4d1-bdaaaee04f56' is of an invalid length for use with domain sockets on this platform.  The length must be between 1 and 104 characters, inclusive. (Parameter 'path')

To mitigate that, we'll need to use shorter application discriminator and instance identifiers (and remove the OpenIddict.Client.SystemIntegration- prefix, potentially).

Additional context

Reported by @xperiandri.