Enable localized check makers for quosure-checks

This issue refers to the development branch.

Example:

chkrs <- localize(isTRUE, "{{.}} not scalar (length is {length(.)})" = {length(.) == 1L})

should produce the list of two functions such that

chkrs[[1]](x, y)
#> ~isTRUE ~ list(`FALSE: isTRUE(x)` = ~x, `FALSE: isTRUE(y)` = ~y)

chkrs[[2]](x, "Not scalar" = y)
#> ~{length(.) == 1L} ~ list(`x not scalar (length is {length(.)})` = ~x, `Not scalar` = ~y)

NB It is crucial that the predicate remains a quosure—it must remember its original scope.

As such, the error message won't be properly interpreted by the current implementation of err_invalid_input(), because that function relies on the flag dot_as_expr which is set by parse_check(), and is invisible in the output, above.

Consequently, the mechanism by which the proper scope of dot-interpolation is identified will need to be adapted to the above behavior of localize().

Solution 1: One possibility would be substitute the function of the boolean flag dot_as_expr with a special (prefix/suffix) “marker” in the error message, which is interpreted by err_invalid_input().
Solution 2: Alternatively, a simpler, but arguably more “hacky,” approach would be endow localized checkers with an additional “global name” attribute that would be interpreted by parse_check() as overriding the value of the argument msg. In this case, it would suffice for chkrs to behave accordingly:
```
chkrs[[1]](x, y)
#> ~isTRUE ~ list(~x, ~y)
#> attr(,"global_name")
#> [1] ""

chkrs[[2]](x, "Not scalar" = y)
#> ~{length(.) == 1L} ~ list(~x, `Not scalar` = ~y)
#> attr(,"global_name")
#> [1] "{{.}} not scalar (length is {length(.)})"
```
No change would then be required elsewhere, and the logic of localize() would be simplified as well, for it would not require any naming logic.

egnha / valaddin

Enable localized check makers for quosure-checks #45