input/csv: extend column-formats support for backwards compatibility

input/csv: extend column-formats support for backwards compatibility

Extend the "column-formats" option support in the CSV input module to
also support wildcards and automatic channel count detection. Move the
format string interpretation to the location where the first data line
or the optional header line are seen. Map the simple options (single
column number and channel count, or first column number and optional
channel count) to a format string, to unify internal code paths. Remove
code paths for the previous specific yet limited scenarios.

Rephrase the condition which keeps executing the "initial receive"
phase. The text line termination sequence gets derived from the first
complete text line, but other essential information is only gathered
later, potentially after skipping a large (user specified) amount of
input data. Keep checking for this essential setup data until data or
the header actually were seen, before regular processing of input data
starts.