[Request] Small grammar edits for querying.

[SalBakraa]

Hi, I am trying to write a highlights.scm query file for this parser so that it works with nvim-treesitter in-place of the current kotlin parser that is shipped with it. The edits needed for this would be:

• [x] Unhide the _line_str_escaped_char and _escape_seq, so that escape sequences can be queried
• [x] !is and ?. are not possible to be queried since they are locked behind the _not_is and _safe_nav rules, unlike is, ?:, in,!in and so on.
• [ ] Separate the labels from labeled jump_expressions. Could be done by adding a simple_identifier child node to jump_expression
• [x] anonymous function parameters and return type are marked as ERROR nodes in the syntax tree