Tracestate - use simple ASCII of tracestate instead of special array format

[SergeyKanzhelev]

As was discussed a few times, special array formatting for tracestate has many drawbacks:

• The need to parse tracestate to convert accross formats - binary to http and back
• There is very small saving on special format. Not enough to justify the different format

So the suggestion is to switch to simple ASCII of tracestate