Investigate AmqpClient accepting a list of str for the desired capabilities

[yunhaoling]

In the current world, AmqpClient only accepts AMQPValue for the desired capabilities:

azure-uamqp-python/uamqp/client.py

Lines 834 to 838 in ec32de9

	:param desired_capabilities: The extension capabilities desired from the peer endpoint.
	To create an desired_capabilities object, please do as follows:
	- 1. Create an array of desired capability symbols: `capabilities_symbol_array = [types.AMQPSymbol(string)]`
	- 2. Transform the array to AMQPValue object: `utils.data_factory(types.AMQPArray(capabilities_symbol_array))`
	:type desired_capabilities: ~uamqp.c_uamqp.AMQPValue

However, this means the upper applications have to construct the AMQPString/AMQPSymbol/AMQPArray/AMQPValue by themselves.

It would be nice if we could considering adding the support to accept just a list of string, and we do the conversion internally.