ChunkAccumulator read and readAll should be static

[scrat98]

Jetty version(s) 12.0.8

Enhancement Description

ChunkAccumulator.read and ChunkAccumulator.readAll methods create AccumulatorTask that's under the hood creates ChunkAccumulator instance and pass it to the take method, therefore I think it's more accurate to make these methods static

[gregw]

@scrat98 please note #11598 which deprecates ChunkAccumulator. It is still draft status, but we are working on improving this area of the code. So until we have decided on that, we are unlikely to make API changes here.

[scrat98]

@gregw then I think we can close this issue if eventually ChunkAccumulator will be removed