[C++] String formatting kernel

[asfimport]

Implement a string formatting kernel. There are several possible designs we could consider for this:

• a variadic kernel that works like fmt::format or std::format in C++20 (probably the best option)
• something more similar to Python str.format
• something more like C++ printf

Reporter: Ian Cook / @ianmcook

Related issues:

• [C++] String algorithm library for StringArray/BinaryArray (is a child of)
• [C++][Compute] Add utf8_format kernel (is duplicated by)
• [C++] Add variadic string join kernel (relates to)
• [R] Bindings for glue() (is depended upon by)

_{Note: This issue was originally created as ARROW-13106. Please see the migration documentation for further details.}

[asfimport]

David Li / @lidavidm:
Duplicate of ARROW-12990 perhaps? Though that one is specified as very limited.

[asfimport]

Joris Van den Bossche / @jorisvandenbossche:
Does the C++20 version allow any formatting of the value that gets inserted? (like a float with ".. \{0:.2f\} ..")

[asfimport]

Ben Kietzman / @bkietz:
C++20's std::format can provide a format specification including "{0:.2f}".

However fmt::format includes named arguements, which I think we'd want to support since extract_regex produces named struct fields.

In the interest of keeping things simple, I'd suggest we import fmt::format's format specification mini language https://fmt.dev/dev/syntax.html#format-string-syntax

[asfimport]

David Li / @lidavidm:
It might be easiest to just vendor fmt in that case? (libfmt.so on conda-forge looks to be 250KB though, so perhaps it's a bit heavy.)