mysql-srv: Correct the size of binary TIME buffers

We were incorrectly setting the size of TIME data types, returned over
the binary (prepared statement) protocol, with a fixed size of 9
bytes. It should be 8 bytes if not sending microseconds, or 12 if
sending microseconds. [0]

[0] https://dev.mysql.com/doc/dev/mysql-server/latest/ \
    page_protocol_binary_resultset.html

Fixes: REA-5961
Release-Note-Core: Fix bug in mysql binary protocol for TIME types
  without microseconds.
Change-Id: I59356596160fd8bbe772d4829b1cfe2680b00f23
Reviewed-on: https://gerrit.readyset.name/c/readyset/+/10280
Tested-by: Buildkite CI
Reviewed-by: Michael Zink <michael.z@readyset.io>

Author: jasobrown-rs

mysql-srv/src/value/encode.rs

@@ -692,7 +692,7 @@ impl ToMySqlValue for Duration {
                 if us != 0 {
                     w.write_u8(12u8)?;
                 } else {
-                    w.write_u8(9u8)?;
+                    w.write_u8(8u8)?;
                 }
 
                 w.write_u8(0u8)?; // positive only (for now)