[pdata] Revisit ValueType.String() output

[dmitryax]

The output of the ValueType.String() is inconsistent with other similar methods. It has 2 issues:

1. After applying [pdata] Revisit need of Val suffix of Value methods #6081, all the string value identifies were consistently renamed to Str. The short name Str is chosen instead of String in order to avoid unintentionally implementing fmt.Stringer interface by string type Value getter. Output of ValueType.String for string type is still STRING which is inconsistent with other types:

ValueTypeEmpty -> "EMPTY"
ValueTypeStr -> "STRING"
ValueTypeBool -> "BOOL"
ValueTypeInt -> "INT"
ValueTypeDouble -> "DOUBLE"
ValueTypeMap -> "MAP"
ValueTypeSlice -> "SLICE"
ValueTypeBytes -> "BYTES"

2. String value returned by pcommon.ValueType.String has been generated by uppercasing type identifiers while other similar methods return identifies as e.g.:

MetricTypeNone -> "None"
MetricTypeGauge -> "Gauge"
MetricTypeSum -> "Sum"
MetricTypeHistogram -> "Histogram"
MetricTypeExponentialHistogram -> "ExponentialHistogram"
MetricTypeSummary -> "Summary"

Suggestion is to change ValueType.String() output to return the string representation of corresponding type identifiers:

ValueTypeEmpty -> "Empty"
ValueTypeStr -> "Str"
ValueTypeBool -> "Bool"
ValueTypeInt -> "Int"
ValueTypeDouble -> "Double"
ValueTypeMap -> "Map"
ValueTypeSlice -> "Slice"
ValueTypeBytes -> "Bytes"

It means we choose consistency over readability ("Str" instead of "String"). I believe it's ok given that we already return "BOOL" not "Boolean" for ValueTypeBool, but I'm open for any other suggestions.

cc @open-telemetry/collector-approvers

[bogdandrutu]

One more enum that we don't do this is plog.SeverityNumber see https:/open-telemetry/opentelemetry-collector/blob/main/pdata/plog/logs.go#L73

Update: an argument can be made that the enums defined in the proto have the String method as the proto string representation, but we don't do that for other places like StatusCode and MetricAggregationTemporality.

[dmitryax]

Makes sense. I'm looking into how the String() method is being used in contrib. I think we can make it shorter and update plog.SeverityNumber accordingly

[bogdandrutu]

Please open a different issue about enums defined in the proto file. The enums Type defined by us are consistent now.

[bogdandrutu]

Also make sure we look at all of them and we come up with the rules

[dmitryax]

Sounds good. Closing this issue in favor of #6251