Fix inconsistent metric types in mysql

Fixes influxdata#8319, influxdata#5711, influxdata#5055, influxdata#7421

See influxdata#5529, influxdata#6624

This could be easily extended to fix influxdata#6671 as well

plugins/inputs/mysql/v2/convert.go

@@ -21,6 +21,10 @@ func ParseInt(value sql.RawBytes) (interface{}, error) {
 	return v, err
 }
 
+func ParseUint(value sql.RawBytes) (interface{}, error) {
+	return strconv.ParseUint(string(value), 10, 64)
+}
+
 func ParseBoolAsInteger(value sql.RawBytes) (interface{}, error) {
 	if bytes.EqualFold(value, []byte("YES")) || bytes.EqualFold(value, []byte("ON")) {
 		return int64(1), nil
@@ -29,6 +33,10 @@ func ParseBoolAsInteger(value sql.RawBytes) (interface{}, error) {
 	return int64(0), nil
 }
 
+func ParseString(value sql.RawBytes) (interface{}, error) {
+	return string(value), nil
+}
+
 func ParseGTIDMode(value sql.RawBytes) (interface{}, error) {
 	// https://dev.mysql.com/doc/refman/8.0/en/replication-mode-change-online-concepts.html
 	v := string(value)
@@ -70,12 +78,27 @@ func ParseValue(value sql.RawBytes) (interface{}, error) {
 }
 
 var GlobalStatusConversions = map[string]ConversionFunc{
-	"ssl_ctx_verify_depth": ParseInt,
-	"ssl_verify_depth":     ParseInt,
+	"innodb_available_undo_logs":    ParseUint,
+	"innodb_buffer_pool_pages_misc": ParseUint,
+	"innodb_data_pending_fsyncs":    ParseUint,
+	"ssl_ctx_verify_depth":          ParseUint,
+	"ssl_verify_depth":              ParseUint,
 }
 
 var GlobalVariableConversions = map[string]ConversionFunc{
-	"gtid_mode": ParseGTIDMode,
+	"delay_key_write":                  ParseString,        // ON, OFF, ALL
+	"enforce_gtid_consistency":         ParseString,        // ON, OFF, WARN
+	"event_scheduler":                  ParseBoolAsInteger, // YES, NO, DISABLED
+	"gtid_mode":                        ParseGTIDMode,
+	"have_openssl":                     ParseBoolAsInteger, // alias for have_ssl
+	"have_ssl":                         ParseBoolAsInteger, // YES, DISABLED
+	"have_symlink":                     ParseBoolAsInteger, // YES, NO, DISABLED
+	"session_track_gtids":              ParseString,
+	"session_track_transaction_info":   ParseString,
+	"slave_skip_errors":                ParseString,
+	"ssl_fips_mode":                    ParseString,
+	"transaction_write_set_extraction": ParseString,
+	"use_secondary_engine":             ParseString,
 }
 
 func ConvertGlobalStatus(key string, value sql.RawBytes) (interface{}, error) {