[ir] Remove std::optional from remapped_entry_point_name #4711

Job	Run time
Go Build and Test	42s
CMake-windows-latest-Debug-msvc	13m 23s
CMake-windows-latest-Release-msvc	16m 51s
CMake-ubuntu-latest-Debug-gcc	20m 57s
CMake-ubuntu-latest-Release-gcc	23m 10s
CMake-macos-latest-Debug-clang	21m 12s
CMake-macos-latest-Release-clang	24m 27s
CMake-macos-13-Debug-clang	42m 29s
CMake-macos-13-Release-clang	54m 46s
	3h 37m 57s

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