Implode tests fail because constructor field has a lexical non-terminal type instead the expected `str`

[jurgenvinju]

Describe the bug

This used to work so I'm adding it back, but the test code seems wrong because implode is not a builtin language feature of Rascal.

Error:  repos/rascal/src/org/rascalmpl/library/lang/rascal/syntax/tests/ImplodeTests.rsc:017:018: Argument 0 should have type `aprod(prod(aadt("Num",[],lexicalSyntax()),[iter(\achar-class([arange(48,57)]),isLexical=true)],alabel="int"),alabel="anonymousint")`, found `str`
Error:  repos/rascal/src/org/rascalmpl/library/lang/rascal/syntax/tests/ImplodeTests.rsc:017:036: Undefined modulevariable, function or constructor `Exp::number`
Error:  repos/rascal/src/org/rascalmpl/library/lang/rascal/syntax/tests/ImplodeTests.rsc:017:048: Argument 0 should have type `aprod(prod(aadt("Num",[],lexicalSyntax()),[iter(\achar-class([arange(48,57)]),isLexical=true)],alabel="int"),alabel="anonymousint")`, found `str`
Error:  repos/rascal/src/org/rascalmpl/library/lang/rascal/syntax/tests/ImplodeTests.rsc:021:019: Argument 0 should have type `aprod(prod(aadt("Number",[],lexicalSyntax()),[iter(\achar-class([arange(48,57)]),isLexical=true)],alabel="int"),alabel="anonymousint")`, found `str`
Error:  repos/rascal/src/org/rascalmpl/library/lang/rascal/syntax/tests/ImplodeTests.rsc:021:040: Undefined modulevariable, function or constructor `Expr::number`
Error:  repos/rascal/src/org/rascalmpl/library/lang/rascal/syntax/tests/ImplodeTests.rsc:021:053: Argument 0 should have type `aprod(prod(aadt("Number",[],lexicalSyntax()),[iter(\achar-class([arange(48,57)]),isLexical=true)],alabel="int"),alabel="anonymousint")`, found `str`
Error:  repos/rascal/src/org/rascalmpl/library/lang/rascal/syntax/tests/ImplodeTests.rsc:036:044: Argument 0 should have type `aprod(prod(aadt("Num",[],lexicalSyntax()),[iter(\achar-class([arange(48,57)]),isLexical=true)],alabel="int"),alabel="anonymousint")`, found `str`
Error:  repos/rascal/src/org/rascalmpl/library/lang/rascal/syntax/tests/ImplodeTests.rsc:040:052: Argument 0 should have type `aprod(prod(aadt("Num",[],lexicalSyntax()),[iter(\achar-class([arange(48,57)]),isLexical=true)],alabel="int"),alabel="anonymousint")`, found `str`
Error:  repos/rascal/src/org/rascalmpl/library/lang/rascal/syntax/tests/ImplodeTests.rsc:044:045: Argument 0 should have type `aprod(prod(aadt("Number",[],lexicalSyntax()),[iter(\achar-class([arange(48,57)]),isLexical=true)],alabel="int"),alabel="anonymousint")`, found `str`
Error:  repos/rascal/src/org/rascalmpl/library/lang/rascal/syntax/tests/ImplodeTests.rsc:048:054: Argument 0 should have type `aprod(prod(aadt("Number",[],lexicalSyntax()),[iter(\achar-class([arange(48,57)]),isLexical=true)],alabel="int"),alabel="anonymousint")`, found `str`
Error:  repos/rascal/src/org/rascalmpl/library/lang/rascal/syntax/tests/ImplodeTests.rsc:054:065: Argument 0 should have type `aprod(prod(aadt("Num",[],lexicalSyntax()),[iter(\achar-class([arange(48,57)]),isLexical=true)],alabel="int"),alabel="anonymousint")`, found `str`
Error:  repos/rascal/src/org/rascalmpl/library/lang/rascal/syntax/tests/ImplodeTests.rsc:058:069: Argument 0 should have type `aprod(prod(aadt("Number",[],lexicalSyntax()),[iter(\achar-class([arange(48,57)]),isLexical=true)],alabel="int"),alabel="anonymousint")`, found `str`

[toinehartman]

I believe the commit that fixed this was reverted, and this issue will be fixed by #2551