fix: BotState cache hash skipped properties

[sw-joelmut]

#minor

Description

This PR fixes an issue where the predefined skipped properties were removed from the bot's state cache object, instead of removing them only from the cache hash calculation because of the original issue (#4325).

Specific Changes

• Updated skipProperties method to not modify the parameter value, and instead generate a copy, so later the hash calculation can use.
• Updated the unit tests for BeginSkill, showing the properties are no longer deleted from the cache.
• Added skillClient to the skipped properties.

Testing

The following image shows the current error, and the bot working from the original issue.

[coveralls]

Pull Request Test Coverage Report for Build 7400583236

• 4 of 4 (100.0%) changed or added relevant lines in 2 files are covered.
• 90 unchanged lines in 7 files lost coverage.
• Overall coverage decreased (-0.03%) to 84.511%

---

Files with Coverage Reduction	New Missed Lines	%
libraries/botbuilder-lg/src/templateExtensions.ts	1	85.34%
libraries/botframework-streaming/src/utilities/createNodeServer.ts	1	82.14%
libraries/botbuilder-dialogs/src/skillDialog.ts	3	84.66%
libraries/botbuilder-dialogs-adaptive/src/actions/beginSkill.ts	5	70.12%
libraries/botframework-streaming/src/namedPipe/namedPipeServer.ts	12	61.64%
libraries/botframework-streaming/src/namedPipe/namedPipeClient.ts	17	45.45%
libraries/botframework-streaming/src/namedPipe/namedPipeTransport.ts	51	34.31%

Totals
Change from base Build 7301953860:	-0.03%
Covered Lines:	20408
Relevant Lines:	22872

---

💛 - Coveralls