WString Fix int64_t

Fixed int64_t String support. Resolves issue #7760.

Background:
sprintf on esp32 doesn't support "%lld" parameter.  It's possible to recompile the underlying libraries to add that option, but I have an easier solution.
This has already been solved in ESP8266 version of WString by replacing sprintf() with itoa/ltoa/lltoa.

This PR does the following:
Fixes integer print issues by replacing sprintf() with itoa/ltoa/lltoa
Moves concat(long long num), concat(unsigned long long num) location (match ESP8266)
Cleans up code formatting (matches ESP8266)
Co-authored-by: NMe No Dev <me-no-dev@users.noreply.github.com>