[OTel] quick fix

[pvital]

• fix: Span duration and start_time when recording. Following the Instana Tracing Specification, the span ts must express the span's start as milliseconds since the Unix epoch, and the span d must be the duration of the span in milliseconds.

• fix(tests): Skipping MySQL Client on MacOS.

[GSVarsha]

Span duration and start_time when recording. Following the Instana Tracing Specification, the span ts must express the span's start as milliseconds since the Unix epoch, and the span d must be the duration of the span in milliseconds.

But that's why we are converting them from nano seconds to milli seconds here, right?

[pvital]

Looks good to me, goodbye MySQL errors 🚀

Sorry, @CagriYonca, but it will be there for a while. I read the wrong line of the documentation, and the calculation is correct, as mentioned by @GSVarsha.

I am canceling this PR.