sql: Add Data Type Formatting Functions

[nvb]

Eventually we are going to want to add support for converting various data types to formatted strings, and from formatted strings back again. Postgres handles this well and provides a lot of detail on the specifics of its implementation here.

• to_char(timestamp, text) sql,builtins: support to_char formatting builtins for timestamp and interval #91156
• to_char(interval, text) sql,builtins: support to_char formatting builtins for timestamp and interval #91156
• to_char(date, text) builtins: implement to_char(date, string) #102787
• to_char(int, text)
• to_char(double precision, text)
• to_char(numeric, text)
• to_date(text, text)
• to_timestamp(text, text)
• to_timestamp(double precision) (builtins: implement to_timestamp #77591)
• to_number(text, text)

gz#10829

Jira issue: CRDB-6199

[JackKrupansky]

PG also has the concept of a pair of I/O Functions for each datatype, one function to parse and one to format. The pg_type table names that pair of I/O functions, as well as a pair of binary send/receive functions.

Ultimately, there are any number of format/parse or serialize/deserialize function pairs. For example, encoding of datum values for storage in the KV store (like the decimal type.)

[jkozlowski]

• to_char(timestamp, text)
• to_char(interval, text)
• to_char(int, text)
• to_char(double precision, text)
• to_char(numeric, text)
• to_date(text, text)
• to_timestamp(text, text)
• to_timestamp(double precision)
• to_number(text, text)