feat: Include HEAD method to http requests

[Jhonatan Sandoval Velasco (JhonatanSVDev)]

#minor

Description

This PR adds the HEAD method in the HttpRequest class and adds the method in every schema

Specific Changes

• Added HEAD method to the HttpRequest method list.
• Added HEAD method to schemas of testing and HttpRequest.

Testing

The following image shows the dialogs unit tests passing after the changes.

[Coveralls (coveralls)]

Pull Request Test Coverage Report for Build 380839

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 9 unchanged lines in 4 files lost coverage.
• Overall coverage increased (+0.009%) to 78.458%

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Files with Coverage Reduction	New Missed Lines	%
/libraries/AdaptiveExpressions/BuiltinFunctions/GetNextViableTime.cs	1	90.91%
/libraries/AdaptiveExpressions/BuiltinFunctions/GetPreviousViableTime.cs	1	90.91%
/libraries/integration/Microsoft.Bot.Builder.Integration.AspNet.Core/ServiceCollectionExtensions.cs	1	93.55%
/libraries/Microsoft.Bot.Builder.Dialogs.Adaptive/Actions/HttpRequest.cs	6	87.93%

Totals
Change from base Build 380329:	0.009%
Covered Lines:	26135
Relevant Lines:	33311

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💛 - Coveralls