Fix SpanToJaegerMapper for short trace id handling

[croissant-sama]

Some systems remove leading zeros from trace IDs. This PR adds support for short trace IDs without leading zeros.
Implemented according to the approach of the Golang library uber/jaeger-client-go.

[croissant-sama]

@sergeyklay
Hi! I've made a small fix. Could you please review my changes?

[sergeyklay]

Hey @croissant-sama ! Thanks a lot for your PR and for taking the time to contribute.

I just wanted to let you know that the current changes are causing a syntax error in the tests, so the CI is failing on all PHP versions. The error message is:

ParseError: syntax error, unexpected ';', expecting variable (T_VARIABLE) in tests/Jaeger/Mapper/SpanToJaegerMapperTest.php:184

It looks like there's a typo in the test file you updated (line 184). Could you double-check that section and fix the syntax error? Once that’s fixed, the CI should pass and I’ll be happy to review your changes again.

NB: I also noticed the workflow was failing because it was using a deprecated version of actions/cache@v2. I went ahead and updated it to v4 in your branch to fix this problem, so you don’t need to worry about that one.

Let me know if you have any questions

[sergeyklay]

The changes currently cause a syntax error in the tests

[croissant-sama]

@sergeyklay I made the necessary fix.

[croissant-sama]

Hey @sergeyklay! Could you please review my changes?

[sergeyklay]

@croissant-sama thank you! Just released new version https://github.com/jonahgeorge/jaeger-client-php/releases/tag/v1.5.2