grpcquick: give each remaining quick test its own QML module URI

The remaining grpc quick autotests (calloptions, channeloptions,
http2channel, metadata) register their QML test module under the shared
URI "QmlTestUri".

Sharing the URI is harmless while each test runs on its own. OpenHarmony
instead deploys all autotests in a single bundle, and we plan to deploy
their QML modules into one shared import directory. Modules that share a
URI would then map to the same path and collide.

Give each test its own URI, GrpcQuickTest.<Test>, and update the
matching QML imports. With this, no qtgrpc QML test registers under
"QmlTestUri" any more.

Task-number: QTBUG-147585
Pick-to: 6.12
Change-Id: I38055cbc3ed565823b3e9ee53b20fbdd5af1482a
Reviewed-by: Dennis Oberst <dennis.oberst@qt.io>