Add support for CTE and CallKit sample refactor

[raosanat]

Purpose

1. Demonstrates CTE (Custom Teams Endpoint) support in ACS SDK.
2. Split samples in to 2 samples. a. CallKit in ACS SDK usage. b. CallKit in ACS and app usage.

Does this introduce a breaking change?

[ ] Yes
[x] No

Pull Request Type

What kind of change does this Pull Request introduce?

[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[x] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ ] Other... Please describe:

How to Test

• Get the code

git clone https://github.com/Azure-Samples/communication-services-ios-quickstarts
cd communication-services-ios-quickstarts
git checkout sanathr/cte_support_v2
pod install 

• Test the code

What to Check

Verify that the following are valid

• ...

Other Information