Refactor formatDate and formatDateShort

[nekiro]

Pull Request Prelude

• I have followed proper The Forgotten Server code styling.
• I have read and understood the contribution guidelines before making this PR.
• I am aware that this PR may be closed if the above-mentioned criteria are not fulfilled.

Changes Proposed

Use fmt in formatDate and formatDateShort

Issues addressed:
None

[ranisalt]

Idea: create macros FMT_DATE_SHORT and FMT_DATE_LONG and use it like that:

#define FMT_DATE_SHORT "{:%d %b %Y}"

...

disconnectClient(fmt::format("Your IP has been banned until " FMT_DATE_SHORT " by {:s}.\n\nReason specified:\n{:s}", fmt::localtime(banInfo.expiresAt), banInfo.bannedBy, banInfo.reason), version);

OR

Create a function formatDate that takes a time_t and a format string:

constexpr std::string_view FMT_DATE_SHORT = "{:%d/%m/%Y %H:%M:%S}"

...

std::string formatDate(time_t time, std::string_view format) {
  return fmt::format(format, fmt::localtime(time));
}

...

formatDate(time, FMT_DATE_SHORT);