Enable Uncurried Mode by Default for Parser Development CLI

[IwanKaramazow]

When debugging the AST through the parser's development CLI, there is a discrepancy between calling dune exec bsc and dune exec res_parser. The former defaults to uncurried mode, while the latter does not.

This commit enables uncurried mode by default for the parser development CLI. If needed, this can be optionally disabled by using the -legacy-curried flag.

[IwanKaramazow]

This also influences the parser/printer tests. I'll change this PR to "enable uncurried by default for the parser/printer tests"

[cknitt]

I think this is obsolete now that v12 is uncurried only and Config.uncurried is gone.