HashMap: Allow hashing of differently typed keys #301

Job	Run time
📊 Static checks / Code style, file formatting, and docs	32s
🍏 iOS / Template (target=template_release)	14m 24s
🐧 Linux / Editor w/ Mono (target=editor)	37m 30s
🤖 Android / Editor (target=editor)	21m 46s
🍎 macOS / Editor (target=editor, tests=yes)	2m 0s
🐧 Linux / Editor with doubles and GCC sanitizers (target=editor, tests=yes, dev_build=yes, scu_build=yes, precision=double, use_asan=yes, use_ubsan=yes, linker=gold)	41m 29s
🤖 Android / Template arm32 (target=template_release, arch=arm32)	14m 33s
🍎 macOS / Template (target=template_release)	1m 55s
🐧 Linux / Editor with clang sanitizers (target=editor, tests=yes, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	35m 44s
🤖 Android / Template arm64 (target=template_release, arch=arm64)	13m 45s
🐧 Linux / Editor with ThreadSanitizer (target=editor, tests=yes, dev_build=yes, use_tsan=yes, use_llvm=yes, linker=lld)	28m 32s
🌐 Web / Template w/ threads (target=template_release, threads=yes)	23m 55s
🐧 Linux / Template w/ Mono (target=template_release)	24m 7s
🌐 Web / Template w/o threads (target=template_release, threads=no)	23m 26s
🐧 Linux / Minimal template (target=template_release, everything disabled)	16m 27s
🏁 Windows / Editor (target=editor, tests=yes)	2m 35s
🏁 Windows / Template (target=template_release)	2m 36s
🪲 Godot CPP / Build and test Godot CPP	8m 4s
	5h 13m 20s

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