[C++][Compute] Support string_view/binary_view in scalar string predicate kernels

### Describe the enhancement requested

The scalar string predicate/measurement kernels return NotImplemented for string_view / binary_view input, so evaluating a string predicate on a view array requires casting the whole column to utf8/binary first.

This adds view support to the kernels that read a string and emit a fixed-width type (no string output):

- match_substring(_regex), match_like, starts_with, ends_with
- find_substring(_regex), count_substring(_regex)
- binary_length, utf8_length
- string_is_ascii, ascii_is_*, utf8_is_*

Kernels that emit strings/lists (utf8_upper/lower/trim*, replace_substring, split_pattern, etc.) are out of scope for a follow-up.

### Component(s)

C++