B3 ArgumentRegValue can encode a register pair on 32-bit

[jjgriego]

f48467a

B3 ArgumentRegValue can encode a register pair on 32-bit
https://bugs.webkit.org/show_bug.cgi?id=257286

Reviewed by NOBODY (OOPS!).

To start to wedge B3 support into the 32-bit port, we need a way to still talk
about the full breadth of B3 values, which includes 64-bit numbers; we need a
way to take these as arguments. Add a constructor for ArgumentRegValue which
denotes a register pair interpreted as a single 64-bit argument.

If we prefer, an alternative would be to add a new Value subclass for this; this
seemed more straightforward.

* Source/JavaScriptCore/b3/B3ArgumentRegValue.cpp:
(JSC::B3::ArgumentRegValue::dumpMeta const):
* Source/JavaScriptCore/b3/B3ArgumentRegValue.h:
* Source/JavaScriptCore/b3/B3Validate.cpp:

f48467a

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[webkit-early-warning-system]

EWS run on current version of this PR (hash f48467a)

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	✅ 🛠 watch		✅ 🛠 jsc-mips
	✅ 🛠 watch-sim		✅ 🧪 jsc-mips-tests

[webkit-early-warning-system]

EWS run on previous version of this PR (hash 333f051)

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⏳ 🧪 style	⏳ 🛠 ios	⏳ 🛠 mac	⏳ 🛠 wpe	⏳ 🛠 wincairo
⏳ 🧪 bindings	⏳ 🛠 ios-sim	⏳ 🛠 mac-AS-debug	⏳ 🧪 wpe-wk2
⏳ 🧪 webkitperl	⏳ 🧪 ios-wk2	⏳ 🧪 api-mac	⏳ 🛠 gtk
	⏳ 🧪 ios-wk2-wpt	⏳ 🧪 mac-wk1	⏳ 🧪 gtk-wk2
⏳ 🛠 🧪 jsc	⏳ 🧪 api-ios	⏳ 🧪 mac-wk2	⏳ 🧪 api-gtk
⏳ 🛠 🧪 jsc-arm64	⏳ 🛠 tv	⏳ 🧪 mac-AS-debug-wk2	✅ 🛠 jsc-armv7
⏳ 🧪 services	⏳ 🛠 tv-sim	⏳ 🧪 mac-wk2-stress	🧪 jsc-armv7-tests
	⏳ 🛠 watch		✅ 🛠 jsc-mips
	✅ 🛠 watch-sim		🧪 jsc-mips-tests