Added unit tests for initializer_list construction #652

Job	Run time
Syntax Check - Clang C++03 Linux No STL (ubuntu-22.04)	1m 0s
Syntax Check - Clang C++03 Linux STL (ubuntu-22.04)	1m 21s
Syntax Check - Clang C++11 Linux No STL (ubuntu-22.04)	1m 1s
Syntax Check - Clang C++11 Linux No STL Force C++03 (ubuntu-22.04)	1m 3s
Syntax Check - Clang C++11 Linux STL (ubuntu-22.04)	1m 32s
Syntax Check - Clang C++11 Linux STL Force C++03 (ubuntu-22.04)	1m 22s
Syntax Check - Clang C++14 Linux No STL (ubuntu-22.04)	1m 3s
Syntax Check - Clang C++14 Linux No STL Force C++03 (ubuntu-22.04)	1m 1s
Syntax Check - Clang C++14 Linux STL (ubuntu-22.04)	1m 19s
Syntax Check - Clang C++14 Linux STL Force C++03 (ubuntu-22.04)	1m 22s
Syntax Check - Clang C++17 Linux No STL (ubuntu-22.04)	1m 12s
Syntax Check - Clang C++17 Linux No STL Force C++03 (ubuntu-22.04)	1m 13s
Syntax Check - Clang C++17 Linux STL (ubuntu-22.04)	1m 17s
Syntax Check - Clang C++17 Linux STL Force C++03 (ubuntu-22.04)	1m 24s
Syntax Check - Clang C++20 Linux No STL (ubuntu-22.04)	1m 0s
Syntax Check - Clang C++20 Linux STL (ubuntu-22.04)	1m 19s
Syntax Check - Clang C++20 Linux No STL Force C++03 (ubuntu-22.04)	1m 5s
Syntax Check - Clang C++20 Linux STL Force C++03 (ubuntu-22.04)	1m 20s
	21m 54s

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