Update Hive schema evolution documentation

[dain]

I happen to be reading the code today, and I think the docs are out of date. The docs seem to be missing:

• varchar <-> timestamp
• varchar -> date
• varchar -> narrower varchar
• char -> narrower char
• double -> float
• decimal -> decimal (looks like narrowing and widening)
• decimal -> double, real, varchar, tinyint, smallint, integer, bigint
• double/real -> decimal

It is strange there is no there is no date to varchar or varchar to decimal.

Maybe we should add a matrix for this?

[mosabua]

Docs are at https://trino.io/docs/current/connector/hive.html#schema-evolution

I will send a PR to update