Improve connection string parsing failure exception

[bgrainger]

At https://stackoverflow.com/questions/59755394/add-record-to-mysql-always-raises-input-string-was-not-in-a-correct-format-er a user posts this exception from having a malformed connection string:

System.FormatException
           at System.Number.StringToNumber(ReadOnlySpan`1 str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal)
           at System.Number.ParseUInt32(ReadOnlySpan`1 value, NumberStyles options, NumberFormatInfo numfmt)
           at System.String.System.IConvertible.ToUInt32(IFormatProvider provider)
           at System.Convert.ChangeType(Object value, Type conversionType, IFormatProvider provider)
           at MySql.Data.MySqlClient.MySqlConnectionStringValueOption`1.ChangeType(Object objectValue) in C:\projects\mysqlconnector\src\MySqlConnector\MySql.Data.MySqlClient\MySqlConnectionStringBuilder.cs:line 703
           at MySql.Data.MySqlClient.MySqlConnectionStringValueOption`1.GetValue(MySqlConnectionStringBuilder builder) in C:\projects\mysqlconnector\src\MySqlConnector\MySql.Data.MySqlClient\MySqlConnectionStringBuilder.cs:line 674
           at MySqlConnector.Core.ConnectionSettings..ctor(MySqlConnectionStringBuilder csb) in C:\projects\mysqlconnector\src\MySqlConnector\Core\ConnectionSettings.cs:line 39
           at MySqlConnector.Core.ConnectionPool.GetPool(String connectionString) in C:\projects\mysqlconnector\src\MySqlConnector\Core\ConnectionPool.cs:line 405
           at MySql.Data.MySqlClient.MySqlConnection.OpenAsync(Nullable`1 ioBehavior, CancellationToken cancellationToken) in C:\projects\mysqlconnector\src\MySqlConnector\MySql.Data.MySqlClient\MySqlConnection.cs:line 292
           at MySql.Data.MySqlClient.MySqlConnection.Open() in C:\projects\mysqlconnector\src\MySqlConnector\MySql.Data.MySqlClient\MySqlConnection.cs:line 280
           at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenDbConnection(Boolean errorsExpected)
           at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.Open(Boolean errorsExpected)
           at Pomelo.EntityFrameworkCore.MySql.Storage.Internal.MySqlRelationalConnection.Open(Boolean errorsExpected)
           at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.BeginTransaction(IsolationLevel isolationLevel)
           at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.BeginTransaction()
           at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.Execute(IEnumerable`1 commandBatches, IRelationalConnection connection)
           at Microsoft.EntityFrameworkCore.Storage.RelationalDatabase.SaveChanges(IList`1 entries)
           at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChanges(IList`1 entriesToSave)
           at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChanges(DbContext _, Boolean acceptAllChangesOnSuccess)
           at Pomelo.EntityFrameworkCore.MySql.Storage.Internal.MySqlExecutionStrategy.Execute[TState,TResult](TState state, Func`3 operation, Func`3 verifySucceeded)
           at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChanges(Boolean acceptAllChangesOnSuccess)
           at Microsoft.EntityFrameworkCore.DbContext.SaveChanges(Boolean acceptAllChangesOnSuccess)
           at Microsoft.EntityFrameworkCore.DbContext.SaveChanges()

This is not an easy exception message or call stack to understand. It would be better to have a message such as "{x} is not a valid value for the {y} connection string option".

[bgrainger]

Connector/NET throws an ArgumentException: "Value 'pants' is not of the correct type."

[bgrainger]

Improved in 0.62.0.