[PORT] update adaptive inputs to set inputHint = expectingInput

[Danieladu]

close: #1776
At first, LG ActivityFactory use MessageFactory.Text() to generate message activity result from LG output, but MessageFactory.Text() would inject inputhint = expectingInput into activity, and the prompt of input relies on this feature.

Then we found there is no reason to add inputhint into pure text activity, so we removed it.

At the same time, we should update adaptive inputs to set inputHint = expectingInput whenever we are issuing a prompt or reprompt (unrecognized/ invalid prompt).

[coveralls]

Pull Request Test Coverage Report for Build 119814

• 0 of 8 (0.0%) changed or added relevant lines in 1 file are covered.
• 10 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-0.09%) to 67.112%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
libraries/botbuilder-dialogs-adaptive/src/input/inputDialog.ts	0	8	0.0%

Files with Coverage Reduction	New Missed Lines	%
libraries/botbuilder-dialogs-adaptive/src/input/inputDialog.ts	1	7.41%
libraries/botframework-streaming/src/webSocket/webSocketTransport.ts	2	80.65%
libraries/botframework-streaming/src/webSocket/webSocketServer.ts	7	66.67%

Totals
Change from base Build 119752:	-0.09%
Covered Lines:	10263
Relevant Lines:	14468

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💛 - Coveralls