LDML: make conf_to_src reuse common data between collations

conf_to_src duplicates the ctype, to_lower, to_upper and tab_to_uni arrays when dumping data from the XML files in /sql/share/charsets/ to ctype-extra.c

For example, the ctype map from cp1251.xml is dumped five times:

static const uchar ctype_cp1251_bulgarian_ci[] = ..

static const uchar ctype_cp1251_ukrainian_ci[] = ..

static const uchar ctype_cp1251_bin[] = ..

static const uchar ctype_cp1251_general_ci[] = ..

static const uchar ctype_cp1251_general_cs[] = ..

After adding MDEV-9711 the number of duplicate data will grow even further two times.

We'll change conf_to_src.c to detect duplicate arrays. Non-primary collations will reuse arrays from the primary collation if the data is the same.