sql: replace type familes with type categories

[mgartner]

Our concept of type families is similar to Postgres's type categories, but the categorizations and behavior are subtly different, resulting in behavior that is inconsistent with Postgres.

From the Postgres docs on type conversion:

An additional heuristic provided by the parser allows improved determination of the proper casting behavior among groups of types that have implicit casts. Data types are divided into several basic type categories, including boolean, numeric, string, bitstring, datetime, timespan, geometric, network, and user-defined. (For a list see Table 52.63; but note it is also possible to create custom type categories.) Within each category there can be one or more preferred types, which are preferred when there is a choice of possible types. With careful selection of preferred types and available implicit casts, it is possible to ensure that ambiguous expressions (those with multiple candidate parsing solutions) can be resolved in a useful way.

There is logic scattered throughout the code base that is related to type families, so this will be a major endeavor. This is a meta issue to track the high-level goal.

Epic CRDB-2474
Jira issue: CRDB-12462