Fix(table_diff): Widen the data types that --decimals applies to

[erindru]

Prior to this, sqlmesh table_diff ... --decimals n would:

• Only apply --decimals to columns of type DOUBLE or FLOAT. I believe the reason was historical - it is assumed that floating point numbers are always awkward so you have to round them to some fixed length out of necessity, but if you're using fixed point numbers then you don't need this so the whole number should be compared
• Assume that every database has a ROUND function that works with floating point types (Postgres is a notable example that does not)

So this PR:

• Updates --decimals to apply to any column that can contain a fixed or floating point decimal
• Uses EngineAdapter._normalize_decimal_value to produce the value to compare instead of wrapping it in ROUND() and hoping that is valid on the target database