[dart2js] crash when using records with null-assertions

[sigmundch]

This program crashes during SSA:

main() => foo((1, 2));
foo((int, int) p) {
  print(p);
}

With the following stack when run as: dart compile js --null-assertions repro.dart

The compiler crashed: UnimplementedError: isNonNullableIfSound (int,int)
#0      DartTypes.isNonNullableIfSound (package:compiler/src/elements/types.dart:2423:5)
#1      KernelSsaGraphBuilder._potentiallyAssertNotNull (package:compiler/src/ssa/builder.dart:1615:20)
#2      KernelSsaGraphBuilder._potentiallyCheckInlinedParameterTypes.<anonymous closure> (package:compiler/src/ssa/builder.dart:6752:11)
#3      forEachOrderedParameter.handleParameter (package:compiler/src/js_model/element_map.dart:602:6)
#4      forEachOrderedParameterByFunctionNode (package:compiler/src/js_model/element_map.dart:574:6)
#5      forEachOrderedParameter (package:compiler/src/js_model/element_map.dart:610:9)
#6      KernelSsaGraphBuilder._potentiallyCheckInlinedParameterTypes (package:compiler/src/ssa/builder.dart:6738:5)
#7      KernelSsaGraphBuilder._visitInlinedFunction (package:compiler/src/ssa/builder.dart:6687:5)
#8      KernelSsaGraphBuilder._doInline (package:compiler/src/ssa/builder.dart:6682:5)
#9      KernelSsaGraphBuilder._doTryInlineMethod.doInlining.<anonymous closure> (package:compiler/src/ssa/builder.dart:6375:11)
#10     KernelSsaGraphBuilder._inlinedFrom.<anonymous closure> (package:compiler/src/ssa/builder.dart:962:21)
#11     DiagnosticReporter.withCurrentElement (package:compiler/src/diagnostics/diagnostic_listener.dart:142:15)
#12     KernelSsaGraphBuilder._inlinedFrom (package:compiler/src/ssa/builder.dart:960:14)
#13     KernelSsaGraphBuilder._doTryInlineMethod.doInlining (package:compiler/src/ssa/builder.dart:6370:7)
#14     KernelSsaGraphBuilder._doTryInlineMethod (package:compiler/src/ssa/builder.dart:6382:7)
#15     KernelSsaGraphBuilder._tryInlineMethod (package:compiler/src/ssa/builder.dart:6135:21)
#16     KernelSsaGraphBuilder._pushStaticInvocation (package:compiler/src/ssa/builder.dart:5321:9)
#17     KernelSsaGraphBuilder.visitStaticInvocation (package:compiler/src/ssa/builder.dart:4248:7)
#18     StaticInvocation.accept (package:kernel/ast.dart:7041:44)

Note that --null-assertions this is only valuable with mixed-mode programs using unsound null safety, so this doesn't affect users of Dart 3 and the fix doesn't need to be cherry-picked.

It does reveal that our compiler still allows using this flag with sound programs, which is unnecessary and may require additional cleanup.