tex-l3kernel-doc: update to 2023.70027

### Changed
- Improve error recovery when an invalid `prop` is used

### Fixed
- Restore `\__kernel_msg_...:nnx(xx)` for older `xparse` support
- Prevent an infinite loop in `\debug_(on|off):n`
- Require `\sys_ensure_backend:` is used in the preamble

### Changed
- Work-around to enable `\prop_set_from_keyval:Nn`, etc., to avoid an error if
  `prop` is not already defined

### Fixed
- Extend debug checking to cover `\prop_(g)set_from_keyval:Nn`

### Added
- Checking missing `\endgroup` at the end of `\DocInclude`
- Linked storage type for large property lists

### Changed
- `\meta` now typesets in `\texttt`, along with `\Arg`
- Improved the performance of `\cs_if_exist:NTF`, `\cs_if_free:NTF`,
    `\cs_if_exist_use:NTF`, and most notably their `c`-type variants.

### Fixed
- Inconsistent local/global assignments in `\vcoffin_gset:Nnn` and
  `\vcoffin_gset:Nnw`
- Tokenization by `\peek_analysis_map_inline:n` of one additional
  character after any space or brace

### Deprecated
- `\msg_gset:nnn(n)`

### Added
- `\keys_set_exclude_groups:nnn(nN)` to replace `\keys_set_filter:nnn(nN)`
- Flags with N-type names, like other variable types

### Changed
- Set `l3doc` option `kernel` off as-standard
- Moved `\seq_set_filter:NNn` to stable

### Deprecated
- `\keys_set_filter:nnn(nN)` in favor of  `\keys_set_exclude_groups:nnn(nN)`

(markd)