backport-2.1: fix the handling of SQL types

[jseldess]

PR: cockroachdb/cockroach#29006

From release notes:

CockroachDB now distinguishes CHAR and VARCHAR, as mandated by the SQL standard and PostgreSQL compatibility. When a width is not specified (e.g., CHAR(3)), the maximum width of VARCHAR remains unconstrained whereas the maximum width of CHAR is 1 character. [#29006][#29006] {% comment %}doc{% endcomment %}

CockroachDB now populates the data_type column of information_schema.columns like PostgreSQL, for compatibility with 3rd party tools and ORMs. [#29006][#29006] {% comment %}doc{% endcomment %}

CockroachDB now preserves the distinction between different column types for string values like in PostgreSQL, for compatibility with 3rd party tools and ORMs. [#29006][#29006] {% comment %}doc{% endcomment %}