Save current tab in `TabBar` and `TabContainer` #14476

Job	Run time
📊 Static checks / Code style, file formatting, and docs	48s
🍏 iOS / Template (target=template_release)	2m 32s
🐧 Linux / Editor w/ Mono (target=editor)	12m 34s
🐧 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)	28m 46s
🤖 Android / Template (target=template_release)	5m 34s
🐧 Linux / Editor with clang sanitizers (target=editor, tests=yes, dev_build=yes, use_asan=yes, use_ubsan=yes, use_llvm=yes, linker=lld)	15m 13s
🐧 Linux / Editor with ThreadSanitizer (target=editor, tests=yes, dev_build=yes, use_tsan=yes, use_llvm=yes, linker=lld)	12m 46s
🌐 Web / Template (target=template_release)	1m 52s
🍎 macOS / Editor (target=editor, tests=yes)	6m 52s
🐧 Linux / Template w/ Mono (target=template_release)	3m 21s
🍎 macOS / Template (target=template_release)	3m 49s
🐧 Linux / Minimal template (target=template_release, everything disabled)	2m 41s
🏁 Windows / Editor (target=editor, tests=yes)	19m 52s
🏁 Windows / Template (target=template_release)	10m 38s
🪲 Godot CPP / Build and test Godot CPP	14m 38s
	2h 21m 56s

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