Support new character sets in MySQL 8.0

[bgrainger]

Run the SideBySide tests against MySQL Server 8.0.1; DataTypes.QueryBinaryGuid(false) fails:

Failed   SideBySide.DataTypes.QueryBinaryGuid(oldGuids: False)
Error Message:
 Assert.Equal() Failure
Expected: typeof(System.Guid)
Actual:   typeof(string)
Stack Trace:
   at SideBySide.DataTypes.QueryBinaryGuid(Boolean oldGuids) in MySqlConnector\tests\SideBySide\DataTypes.cs:line 346

Note that this failure doesn't happen when running just the QueryBinaryGuid tests, nor when setting csb.MaximumPoolSize = 1234; in the test, which indicates it may be related to pulling an existing connection from the pool.

The failure also doesn't reproduce when using MySql.Data 6.9.9.

[bgrainger]

For a passing test, the values on line 337 are:

ColumnLength	CharacterSet	BytesPerCharacter	Computed Length	Correct
144	Utf8Mb4Binary	4	36	✔️

For a failing test, they are:

ColumnLength	CharacterSet	BytesPerCharacter	Computed Length	Correct
144	255	1	144	❌

It appears that MySQL 8.0 has new characters sets that we need to support. Specifically, SELECT id, collation_name FROM information_schema.collations WHERE id > 250 ORDER BY id; lists 43 new character sets.

[bgrainger]

Fixed in 0.18.1.