Initial API

[matthewhilton]

Changes

• Adds API class, which is for general CRUD operations.
• Adds stream wrapper class, which is based off the one from https://github.com/catalyst/moodle-tool_objectfs/blob/MOODLE_402_STABLE/classes/local/store/azure/stream_wrapper.php but cleaned up and tweaked a bit with more comments added.

Notes

• I made the decision to move the stream wrapper here and out of objectfs, since this follows the same pattern that AWS does (the AWS sdk includes a stream wrapper) - nothing about the stream wrapper is objectfs specific.

To Do:

• [y] Testing - Passes integration test + manual testing
• [y] Add Github CI