using hex string as bindvar for decimal type column in prepared statement causes panic

[jennifersp]

Repro enginetest:

{
	Name: "simple decimal type insert",
	SetUpScript: []string{
		"CREATE TABLE test(id int primary key auto_increment, decimal_col DECIMAL(9,2))",
	},
	Assertions: []queries.ScriptTestAssertion{
		{
			Query: "INSERT INTO test(decimal_col) VALUES (?)",
			Bindings: map[string]sql.Expression{
				"v1": expression.NewLiteral([]byte("X'10'"), sql.MustCreateString(sqltypes.VarBinary, 4, sql.Collation_binary)),
			},
			Expected: []sql.Row{
				{sql.OkResult{RowsAffected: 1, InsertID: 1}},
			},
		},
	},
},

Using Literal of X'10' with VarBinary type is because most types are handled as VarBinary in https://github.com/dolthub/vitess/blob/main/go/mysql/query.go#L842 when we get parse the bindvars, so the hex string is handled the same way as any other string values.