attribute: change INVALID Type to EMPTY and mark INVALID as deprecated (#8038)

Fixes https://github.com/open-telemetry/opentelemetry-go/issues/7932

Noticeable comment from previous PR:
https://github.com/open-telemetry/opentelemetry-go/pull/7942#discussion_r2913179215

Print the empty value as empty string per
https://opentelemetry.io/docs/specs/otel/common/#empty-values

log/keyvalue.go

@@ -390,7 +390,7 @@ func (a KeyValue) String() string {
 // ValueFromAttribute converts [attribute.Value] to [Value].
 func ValueFromAttribute(value attribute.Value) Value {
 	switch value.Type() {
-	case attribute.INVALID:
+	case attribute.EMPTY:
 		return Value{}
 	case attribute.BOOL:
 		return BoolValue(value.AsBool())