Using .. for Open Records and ..a for Constrained Records in Types

[smores56]

Currently, we use the following syntax for denoting openness/constraint in record types:

OpenRecord1 a : { foo : a, bar : Str }*
OpenRecord2 a : {
    foo : a,
    bar : Str,
}*

ConstrainedRecord1 a b : { foo : a, bar : Str }b
ConstrainedRecord2 a b : {
    foo : a,
    bar : Str,
}b

We want to move to supporting the following syntax instead:

OpenRecord1 a : { foo : a, bar : Str, .. }
OpenRecord2 a : {
    foo : a,
    bar : Str,
    ..
}*

ConstrainedRecord1 a b : { foo : a, bar : Str, ..b }
ConstrainedRecord2 a b : {
    foo : a,
    bar : Str,
    ..b
}

Though we will likely eventually commit to just this new syntax, there is a lot of Roc code that currently implements the first syntax. Ideally, an implementer would support parsing of either of these syntaxes (but only one or the other should be allowed at once), and then format to the new syntax for minimal, automatic effort on the part of Roc devs.