[RUM-1830] 128 bit trace IDs

[marco-saia-datadog]

What does this PR do?

Introduces 128 bit trace IDs.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests
• Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)
• If this PR is auto-generated, please make sure also to manually update the code related to the change

[ganeshnj]

Some suggestions, overall on right track.

One thing that I couldn't see how we are dealing with RUM, Trace or Log events with this update. I assume some encode/decode to be changed.

[marco-saia-datadog]

I have changed the implementation, here is how it works now:

Separating Span ID and Trace ID

The TracingIdentifier constructor is now private.

It can only be created through TracingIdentifier.createSpanId() or TracingIdentifier.createTraceId(), and it returns different types respectively.

Span IDs will always be generated as 64 bits BigInt(s) and Trace IDs as 128 bits BigInt(s)

String representation takes into account the type of Tracing Identifier

TracingIdFormat (previously TracingIdRepresentation) is now more generic, and the .toString implementation has been modified accordingly.

When requesting a padded HEX value, the bit length of the current type will be taken into account.

Requesting the low bits of a 128 bit Trace ID will get you a 64 bit ID, while requesting the low bits of a 64 bit Span ID will get you a 32 bit ID.

Here is a runnable example.

Here is an example output for reference:

FORMAT	VALUE
Trace ID FULL HEX	667ed836000000000d8dbaedc8adcf59
Trace ID PADDED FULL HEX:	667ed836000000000d8dbaedc8adcf59
Trace ID HIGH HEX	667ed83600000000
Trace ID PADDED HIGH HEX:	667ed83600000000
Trace ID LOW HEX	d8dbaedc8adcf59
Trace ID PADDED LOW HEX:	0d8dbaedc8adcf59
Span ID FULL HEX	378ad79b0519da05
Span ID PADDED FULL HEX	378ad79b0519da05
Span ID HIGH HEX	378ad79b
Span ID PADDED HIGH HEX	378ad79b
Span ID LOW HEX	519da05
Span ID PADDED LOW HEX	0519da05

I will add a few more tests to match the RFC specs more accurately, and verify @ganeshnj's comment #680 (review).

[marco-saia-datadog]

Example of generated headers:

Header	Value
x-datadog-origin	rum
x-datadog-sampling-priority	1
x-datadog-trace-id	17731188736533748218
x-datadog-parent-id	17034905968583185706
x-datadog-tags	_dd.p.tid=6682b2ee00000000
traceparent	00-6682b2ee00000000f611d636468059fa-ec6824b93f95152a-01
tracestate	dd=s:1;o:rum;p:ec6824b93f95152a
b3	6682b2ee00000000f611d636468059fa-ec6824b93f95152a-1
X-B3-TraceId	6682b2ee00000000f611d636468059fa
X-B3-SpanId	ec6824b93f95152a
X-B3-Sampled	1

[ganeshnj]

Nice updates, just a few improvement comments but looks good to me.