[depend #3892] Deprecate xdrlib TRRFile.read() and XTCFile.read() in favour of read_direct methods with memoryview inputs

[hmacdope]

Is your feature request related to a problem?

The TRRFile and XTCFile cython classes currently allocate and return buffers in their respective read() methods.
This is being augmented with methods that read directly into ts.positions, ts.velocities etc directly using memoryviews in #3892 (see read_direct series of methods.)

Describe the solution you'd like

These methods should be deprecated in favour of the more efficient read_direct series of methods. that use memoryviews.

However libmdaxdr is semi-public, so it will require a deprecation warning.