Add more efficient function for formatting integer values as strings.
A benchmark shows that using this function is significantly faster than using `str_format`. It is faster by a factor of 220 with Clang 15.0 O2 (https://quick-bench.com/q/BlNoLnlyqxipf4jvsFTUxKMHDJU) and by a factor of 11 with GCC 12.2 O2 (https://quick-bench.com/q/Fxf9lDCTqXBF4pIa_IyZ5R0IqYg).
This increases FPS in the editor by ~25% when many numbers are rendered for switch/tele/speedup/tune layers or with "Show Info" being enabled.
The additional static analysis for `std::to_chars` revealed that the wrong size was used in `CHud` for `aScoreTeam[TEAM_RED]` and `aScoreTeam[TEAM_BLUE]`.
This requires incrementing the macOS deployment target from 10.13 to 10.15.
Port the `CJsonWriter` utility class from upstream, which makes outputting correct JSON easier.
Add `CJsonWriter` as an abstract class that can write to different outputs. Two implementations `CJsonFileWriter` (writes to a file) and `CJsonStringWriter` (writes to an `std::string`) are added. Upstream `CJsonWriter` can only write to files.
The same tests are added for both implementations. Duplicate code is avoided by using typed tests with two separate test fixtures.
