Improve the string concatenate logic in ToLineProtocol function

[cloudxxx8]

🚀 Feature Request

Relevant Package [REQUIRED]

This feature request is for all

Description [REQUIRED]

The current string concatenate logic could be improved by string builder
https://pkg.go.dev/strings#Builder

Using lots of += in string is not a good practice.

go-mod-core-contracts/dtos/metric.go

Lines 112 to 126 in f15f824

	for _, field := range m.Fields {
	// Fields section doesn't have a leading comma per syntax above so need to skip the comma on the first field
	if isFirst {
	isFirst = false
	} else {
	fields += ","
	}
	fields += fmt.Sprintf("%s=%s", field.Name, formatLineProtocolValue(field.Value))
	}
	// Tags section does have a leading comma per syntax above
	tags := ""
	for _, tag := range m.Tags {
	tags += fmt.Sprintf(",%s=%s", tag.Name, tag.Value)
	}