chore!(outbound-pg): Drop int8 support

There are a few reasons to do this:
- the only pg type that fits into 1 byte is special "char" type which
isn't intended for general-purpose use[1];
- naming is confusing: in the SDK it makes sense to decode it into i8
but in fact it has to be decoded into char;
- in fact, it was never supported - there is no code to decode/encode
it and such columns handled as DbValue::Unsupported/DbDataType::Other;

[1]: https://www.postgresql.org/docs/current/datatype-character.html

Author: etehtsea

crates/outbound-pg/src/lib.rs

@@ -101,7 +101,6 @@ fn to_sql_parameter<'a>(value: &'a ParameterValue) -> anyhow::Result<&'a (dyn To
         ParameterValue::Boolean(v) => Ok(v),
         ParameterValue::Int32(v) => Ok(v),
         ParameterValue::Int64(v) => Ok(v),
-        ParameterValue::Int8(v) => Ok(v),
         ParameterValue::Int16(v) => Ok(v),
         ParameterValue::Floating32(v) => Ok(v),
         ParameterValue::Floating64(v) => Ok(v),

wit/ephemeral/rdbms-types.wit

@@ -1,6 +1,5 @@
 enum db-data-type {
     boolean,
-    int8,
     int16,
     int32,
     int64,
@@ -17,7 +16,6 @@ enum db-data-type {
 
 variant db-value {
     boolean(bool),
-    int8(s8),
     int16(s16),
     int32(s32),
     int64(s64),
@@ -35,7 +33,6 @@ variant db-value {
 
 variant parameter-value {
     boolean(bool),
-    int8(s8),
     int16(s16),
     int32(s32),
     int64(s64),