Span attributes are truncated by number of bytes not number of characters

[MrAlias]

Adding an attribute of a span with the string value こんにちは and an attribute value length of 3 set will result in the attribute value being こ. It should be こんに according to the OTel specification:

• set an attribute value length limit such that for each attribute value:
  • if it is a string, if it exceeds that limit (counting any character in it as 1), SDKs MUST truncate that value, so that its length is at most equal to the limit,