Add "utf-8" as an output mode to the follow tap for tshark.
This produces the same output that the Qt version does (passing
through all valid UTF-8, including control codes and internal
NULs, substituting illegal UTF-8 sequences with REPLACEMENT CHARACTER,
and not handling UTF-8 sequences split between unreassembled frames),
except for some differences which are common to how the tshark
and Wireshark Follow output differs for ASCII and EBCDIC as well:
Tshark includes additional header information and a line length
before each section of output, and leaves end-of-line terminators
untouched; Wireshark, due to the use of Qt code, automatically
translates end-of-line terminators to a LF (including from, e.g.
HTTP), except in "raw" mode. Neither tshark nor Wireshark write
in text mode, i.e. translate end of line terminators to a platform
specific CRLF on Windows.
Related to #19280
1839374fc8