append unit to otel attributes

[KyleAMathews]

e.g. for decode_message_duration I don't know if this is ms or (probably) μs

Appending the unit is needed whenever it's ambiguous.

[kevin-dp]

It's in microseconds. I'm not sure about appending the unit. I think it's better to keep it as a number such that we can query using arithmetic operators and perhaps add the unit in the attribute name.

[KyleAMathews]

Right yeah, append the unit to the attribute name so decode_message_duration_μs