Add cancellation support to all async operations

[ramya-rao-a]

Description

Brief description of the changes made in the PR. This helps in making better changelog

• This PR adds support for cancelling all the async operations via the use of the standard AbortSignalLike interface
• This mainly involves clearing the associated timer at its base, followed by any other clean up that is needed.

Few design discussions:

• AbortSignalLike interface is redefined in this PR instead of relying on an Azure scoped package like @azure/abort-controller which is used in the tests
• I refrained from redefining the AbortError class due to potential conflicts with upstream usage. Instead, using same old Error class with custom name. This is definitely open for debate as to how we should approach this.

Reference to any github issues

• 48

[ramya-rao-a]

cc @richardpark-msft, @HarshaNalluru

[chradek]

I looked into why the CI is failing for this PR. It looks like the new tests don't set reconnect: false on the connections they create. When I ran the tests locally I found there were 2 timers hanging around related to rhea's built in reconnect logic. When I set reconnect to false for all the added tests those timers went away.

I didn't dig into exactly which tests were still allowing reconnects to occur, maybe there are some that don't explicitly close the connection so rhea attempts to reconnect.

[ramya-rao-a]

yay! Thanks for the hint @chradek! Tests are green now

[HarshaNalluru]

Please add changelog