Resolve syntax (printer) bugs for v12

[cknitt]

This is an umbrella issue.
There are quite a few known bugs in the printer that we should aim to resolve for v12.

See https://github.com/rescript-lang/rescript-compiler/issues?q=is%3Aopen+is%3Aissue+label%3Asyntax+label%3Abug

• Comment formatted away in uncurried mode #6890
• Reformatting to invalid code in tests #6966
• Unstable formatting of comments #6976
• Can't add doc comment for a type definition using and #6844
• Parentheses incorrectly removed by printer, leading to wrong application of @uncurry #6784
• Escape character / doesn't work in rescript 10 in %raw templates #6236
• Syntax: E notation check is missing #6986
• Print :> without wrapping parenthesis #6254
• Doc comment affects formatting of attributes #6302
• Comments formatted away when commenting out function params #7085