[exporter/prometheusremotewrite] feat: build prometheus unit and add to metadata in prometheusremotewr…

[alexylew]

…ite exporter

Description

This change adds the logic to convert an OTLP metric unit into the corresponding Prometheus metric unit. It will attempt to map UCUM units to Prometheus units where applicable. This change also extends the metadata emitted by the prometheusremotewrite exporter to include the newly calculated unit.

Link to tracking issue

Fixes #29452

Testing

Added unit tests for the new normalize_unit.go file and also extended some existing unit tests to include more unit types.

Documentation

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: alexylew / name: Alex Lew (0037061, 573a7ab, 5310d55, 42945b6)

[crobert-1]

Hello @alexylew, thanks for your contribution! To be able to move this PR forward, please sign the CLA.

[alexylew]

yup working on getting the CLA signed, waiting for the CLA manager at my org to approve

[alexylew]

/fix:all

[alexylew]

@jmichalek132 or @dashpole if you have a chance to take a look at this PR that'd be much appreciated! This is my first contribution to opentelemetry so not super familiar with all the internal structure yet.