arrow

ARROW-9856: [R] Add bindings for string compute functions

Includes dependency toolchain updates (utf8proc, re2) and bindings for

* "nchar", "str_length" -> "binary_length"
* "tolower", "str_to_lower"  -> "utf8_lower"
* "toupper", "str_to_upper" -> "utf8_upper"
* "str_trim" is handled a little differently since it's one function in `stringr` but three functions in arrow (utf8_ltrim_whitespace, utf8_rtrim_whitespace, utf8_trim_whitespace)

Closes #9423 from nealrichardson/r-strings

Authored-by: Neal Richardson <neal.p.richardson@gmail.com>
Signed-off-by: Neal Richardson <neal.p.richardson@gmail.com>