QDebug: add encoding information to quoted-string outout

For streaming of QAnyStringView to QDebug, we have decided to add encoding information to the quoted string: "..."_L1", u8"...", u"..." (U"...", once char32_t is supported).

It would make sense to use these monikers for all quoted string QDebug output, with a new (no)quote()/(no)space()-like mechanism to enable/disable them in the output.

Acceptance criteria:

• stream output indicates string encoding when quote()'ed:
  • "..."_L1, u8"...", u"...", (U"...", once supported)
• (no)/{space,quote}-like flag to control the feature
  • default off for normal strings, default on for QAnyStringView