Implement constant evaluation in patterns

[chloestefantsova]

The following tests fail due to the absent constant evaluation in patterns:

• co19/LanguageFeatures/Patterns/constant_A03_t03
• co19/LanguageFeatures/Patterns/constant_A03_t06
• co19/LanguageFeatures/Patterns/map_A01_t01
• co19/LanguageFeatures/Patterns/constant_A03_t07
• co19/LanguageFeatures/Patterns/constant_A04_t01
• co19/LanguageFeatures/Patterns/constant_A04_t02

Consider the following program as an example:

String test(List value) {
  if (value case const <int>[1, 2]) {
    return "[1, 2]";
  }
  return "other";
}

main() {
  print(test(const <int>[1, 2]));
}

When complied to Kernel currently, only one of const <int>[1, 2] is represented as a constant.

library /*isNonNullableByDefault*/;
import self as self;
import "dart:core" as core;

static method test(core::List<dynamic> value) → core::String {
  final core::List<dynamic> #t1 = value;
  if(#t1 =={core::List::==}{(core::Object) → core::bool} core::_GrowableList::_literal2<core::int>(1, 2)) {
    {
      return "[1, 2]";
    }
  }
  return "other";
}
static method main() → dynamic {
  core::print(self::test(#C3));
}
constants  {
  #C1 = 1
  #C2 = 2
  #C3 = <core::int*>[#C1, #C2]
}

It prevents the equality to work for constants as expecting, resulting in failing tests. When the program shown above is run, it prints other.

[johnniwinther]

Related to #50629

[johnniwinther]

This seems to have been fixed together with #50629