If TOC writing hits TOC file conflict it tries to throw an exception
with sstable generation in it. However, generation_type is not
formattable at all, let alone the {:d} option.pick
This bug generates an obscure 'fmt::v9::format_error (invalid type
specifier)' error in unknown location making the debugging hard.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Closes#12671