etl/delegate: fix accident creation of a delegate to an rvalue delegate when copying/assigning from delegate with mismatching signature #478

Job	Run time
Syntax Check - Clang C++03 Linux No STL (ubuntu-22.04)	26s
Syntax Check - Clang C++03 Linux STL (ubuntu-22.04)	24s
Syntax Check - Clang C++11 Linux No STL (ubuntu-22.04)	37s
Syntax Check - Clang C++11 Linux No STL Force C++03 (ubuntu-22.04)	35s
Syntax Check - Clang C++11 Linux STL (ubuntu-22.04)	46s
Syntax Check - Clang C++11 Linux STL Force C++03 (ubuntu-22.04)	36s
Syntax Check - Clang C++14 Linux STL (ubuntu-22.04)	41s
Syntax Check - Clang C++14 Linux No STL (ubuntu-22.04)	39s
Syntax Check - Clang C++14 Linux STL Force C++03 (ubuntu-22.04)	41s
Syntax Check - Clang C++14 Linux No STL Force C++03 (ubuntu-22.04)	41s
Syntax Check - Clang C++17 Linux No STL (ubuntu-22.04)	50s
Syntax Check - Clang C++17 Linux No STL Force C++03 (ubuntu-22.04)	1m 1s
Syntax Check - Clang C++17 Linux STL (ubuntu-22.04)	55s
Syntax Check - Clang C++17 Linux STL Force C++03 (ubuntu-22.04)	1m 14s
Syntax Check - Clang C++20 Linux No STL (ubuntu-22.04)	1m 3s
Syntax Check - Clang C++20 Linux No STL Force C++03 (ubuntu-22.04)	1m 11s
Syntax Check - Clang C++20 Linux STL (ubuntu-22.04)	1m 13s
Syntax Check - Clang C++20 Linux STL Force C++03 (ubuntu-22.04)	1m 27s
	15m 0s

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