feat(telemetrygen): added support for delta temporality

[NickAnge]

Description

This PR adds support for configuring metric temporality (delta or cumulative) in the telemetrygen tool. This allows users to generate metrics with different temporality types, which is particularly useful for testing different metric collection scenarios.

Changes

• Added temporalityType flag for metrics pipeline that accepts values: delta or cumulative

Link to tracking issue

Fixes #38073

Testing

Testing was performed by setting up as simple collector with otlp receiver and debug exporter

Sum Datapoint

Resource SchemaURL: https://opentelemetry.io/schemas/1.13.0
Resource attributes:
     -> service.name: Str(telemetrygen)
ScopeMetrics #0
ScopeMetrics SchemaURL: 
InstrumentationScope  
Metric #0
Descriptor:
     -> Name: gen
     -> Description: 
     -> Unit: 
     -> DataType: Histogram
     -> AggregationTemporality: Delta

Histogram Datapoint

Count: 0
Sum: 3940.000000
ExplicitBounds #0: 0.000000
ExplicitBounds #1: 5.000000
ExplicitBounds #2: 10.000000
ExplicitBounds #3: 25.000000
ExplicitBounds #4: 50.000000
ExplicitBounds #5: 75.000000
ExplicitBounds #6: 100.000000
ExplicitBounds #7: 250.000000
ExplicitBounds #8: 500.000000
ExplicitBounds #9: 750.000000
ExplicitBounds #10: 1000.000000
ExplicitBounds #11: 2500.000000
ExplicitBounds #12: 5000.000000
ExplicitBounds #13: 7500.000000
ExplicitBounds #14: 10000.000000
Buckets #0, Count: 0
Buckets #1, Count: 0
Buckets #2, Count: 1
Buckets #3, Count: 0
Buckets #4, Count: 0
Buckets #5, Count: 0
Buckets #6, Count: 3
Buckets #7, Count: 4
Buckets #8, Count: 1
Buckets #9, Count: 1
Buckets #10, Count: 0
Buckets #11, Count: 0
Buckets #12, Count: 0
Buckets #13, Count: 0
Buckets #14, Count: 0

• Need to add tests for the config

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: NickAnge / name: Nikos Angelopoulos (c736320, 6ff6536, aba04c2, 56f210f)

[ArthurSens]

Thank you @NickAnge! Could you take care of CLA? Here are docs that could help you: https://github.com/open-telemetry/community/blob/main/guides/contributor/CLA.md

I know you did some research here, as we have spoken through Slack, and I couldn't answer you. @mx-psi, we were in doubt if, when using deltas, the StartTimestamp should be updated for every datapoint or if we could re-use the same StartTimestamp from the first data point. Could you clarify? While you're at it could you trigger the tests? :)

[mx-psi]

I know you did some research here, as we have spoken through Slack, and I couldn't answer you. @mx-psi, we were in doubt if, when using deltas, the StartTimestamp should be updated for every datapoint or if we could re-use the same StartTimestamp from the first data point. Could you clarify? While you're at it could you trigger the tests? :)

The gist of it is that Deltas update StartTimestamp every time, Cumulative keeps the first one. Which means that the current code is not consistent with an usual cumulative timeseries

[NickAnge]

Thanks @mx-psi and @ArthurSens . I saw your comment at the issue. Will raise an issue for the cumulative "bug" then. I think the PR is ready for review. Will really appreciate your input.