fix(flight): make StreamChunksFromReader ctx aware and cancellation-safe

[arnoldwakim]

Rationale for this change

StreamChunksFromReader previously did not observe context cancellation. As a result, if a client disconnected early, the reader could continue producing data indefinitely, potentially blocking on channel sends, leaking RecordBatch objects, leaking the reader, and consuming unbounded memory and CPU (this observation triggered this PR).

This fix ensures that data streaming promptly stops when the client disconnects.

What changes are included in this PR?

• StreamChunksFromReader now accepts a context.Context.
• Tiny change was made to DoGet, to ensure it continues to work with the context-aware StreamChunksFromReader.

Are these changes tested?

• To be removed from description: the tests are bit tricky to write, similar to that of fix(arrow/flight/flightsql): drain channel in flightSqlServer.DoGet #437. Maybe @zeroshade has suggestions?

Are there any user-facing changes?

• StreamChunksFromReader now accepts a context.Context.

[zeroshade]

Is there any reasonable way to add a test for this?

[arnoldwakim]

I have used a callbackRecordReader reader to test that the new behaviour is okay.
Kindly let me know if this is what you expected.