Feature request for a new collation

Adds more tests for collations
Marks unstable collation tests.
Removes a duplicate test

Closes #4007

@TarantoolBot document
Title: New collations

The recent commit includes a wide variety of collations.
The naming of the new collations have the following principles:
unicode_<locale>_<strength>
Three strengths are used:
Primary - "s1
Secondary - "s2" and
Tertiary - "s3".

The following list contains a so called "stable" collations -
the ones whose sort order doesn't depend on the ICU version:

unicode_am_s3
unicode_fi_s3
unicode_de__phonebook_s3
unicode_haw_s3
unicode_he_s3
unicode_hi_s3
unicode_is_s3
unicode_ja_s3
unicode_ko_s3
unicode_lt_s3
unicode_pl_s3
unicode_si_s3
unicode_es_s3