Simplify translatable messages for tuple value details in conflict.c.

Simplify translatable messages for tuple value details in conflict.c.

append_tuple_value_detail() constructed user-visible messages using
separately translated fragments such as ": ", ", ", and ".",. This
makes correct translation difficult or impossible in some languages.

Refactor append_tuple_value_detail() to move all punctuation and
sentence construction to the callers, which now use a single
translatable string with a %s placeholder for the tuple data.

Reported-by: David Rowley <dgrowleyml@gmail.com>
Author: vignesh C <vignesh21@gmail.com>
Reviewed-by: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Reviewed-by: Zhijie Hou <houzj.fnst@fujitsu.com>
Reviewed-by: Peter Smith <smithpb2250@gmail.com>
Discussion: https://postgr.es/m/227279.1775956328%40sss.pgh.pa.us#8f3a5f50543556c60cc5a13270cb7ba4
Discussion: https://postgr.es/m/CAApHDvohYOdrvhVxXzCJNX_GYMSWBfjTTtB6hgDauEtZ8Nar2A@mail.gmail.com