…ed` getter

This getter was only invoked from `src/display/network.js` and `src/core/chunked_stream.js`, however in both cases it's hardcoded to `false` and thus isn't actually needed.
This originated in PR 6879, close to a decade ago, for a potential TODO which was never implemented and it ought to be OK to just simplify this now.

…eReader`-instance, in the `ChunkedStreamManager` class

Given that nothing in the `PDFWorkerStreamRangeReader` class attempts to invoke the `onProgress` callback, this is effectively dead code now.
Looking briefly at the history of this code it's not clear, at least to me, when this became unused however it's probably close to a decade ago.

Finally, note also how progress is already being reported through the `ChunkedStreamManager.prototype.onReceiveData` method.

…erface

Note how there's *nowhere* in the code-base where the `IPDFStreamRangeReader.prototype.onProgress` callback is actually being set and used, however the loadingBar (in the viewer) still works just fine since loading progress is already reported via:
 - The `ChunkedStreamManager` instance respectively the `getPdfManager` function, through the use of a "DocProgress" message, on the worker-thread.
 - A `IPDFStreamReader.prototype.onProgress` callback, on the main-thread.

Furthermore, it would definitely *not* be a good idea to add any `IPDFStreamRangeReader.prototype.onProgress` callbacks since they only include the `loaded`-property which would trigger the "indeterminate" loadingBar (in the viewer).

Looking briefly at the history of this code it's not clear, at least to me, when this became unused however it's probably close to a decade ago.

…implementations inherit from

Given that there's no less than *five* different, but very similar, implementations this helps reduce code duplication and simplifies maintenance.

Also, spotted during rebasing, pass the `enableHWA` option "correctly" (i.e. as part of the existing `transportParams`) to the `WorkerTransport`-class to keep the constructor simpler.

…reamReader` implementations inherit from

Given that there's no less than *five* different, but very similar, implementations this helps reduce code duplication and simplifies maintenance.

Also, remove the `rangeChunkSize` not defined checks in all the relevant stream-constructor implementations.
Note how the API, since some time, always validates *and* provides that parameter when creating a `BasePDFStreamReader`-instance.

…PDFStreamRangeReader` implementations inherit from

Given that there's no less than *five* different, but very similar, implementations this helps reduce code duplication and simplifies maintenance.