Prometheus exporter emits invalid characters in target_info metric

[Jdsleppy]

Describe your environment

$ python
Python 3.11.2 (main, Feb 17 2023, 09:28:16) [GCC 8.5.0 20210514 (Red Hat 8.5.0-18)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import platform
>>> platform.platform()
'Linux-6.5.6-76060506-generic-x86_64-with-glibc2.28'

Prometheus version 2.46.0

opentelemetry-distro = "0.42b0"
opentelemetry-exporter-prometheus = "==0.42b0"
...

Steps to reproduce
Allow autoinstrumentation to set up the Prometheus metrics exporter

OTEL_SERVICE_NAME=myservice
OTEL_METRICS_EXPORTER=prometheus
OTEL_EXPORTER_PROMETHEUS_PORT=9464
OTEL_EXPORTER_PROMETHEUS_HOST=0.0.0.0

Verify that metrics are exposed:

$ http http://127.0.0.1:9464 | head
# HELP python_gc_objects_collected_total Objects collected during gc
# TYPE python_gc_objects_collected_total counter
python_gc_objects_collected_total{generation="0"} 1.025664e+06
python_gc_objects_collected_total{generation="1"} 277619.0
python_gc_objects_collected_total{generation="2"} 27443.0
# HELP python_gc_objects_uncollectable_total Uncollectable objects found during GC
# TYPE python_gc_objects_uncollectable_total counter
python_gc_objects_uncollectable_total{generation="0"} 0.0
python_gc_objects_uncollectable_total{generation="1"} 0.0
python_gc_objects_uncollectable_total{generation="2"} 0.0
...

Have Prometheus pull metrics from port 9464.

What is the expected behavior?
I expect all the metrics to be pulled into Prometheus without error.

What is the actual behavior?
Prometheus errors when parsing the target_info metric

expected equal, got "." ("INVALID") while parsing: "target_info{service."

$ http http://127.0.0.1:9464 | grep target_info
# HELP target_info Target metadata
# TYPE target_info gauge
target_info{service.name="myservice",telemetry.auto.version="0.42b0",telemetry.sdk.language="python",telemetry.sdk.name="opentelemetry",telemetry.sdk.version="1.21.0"} 1.0

Additional context
The regex given by Prometheus to describe valid label names does not allow for . characters like this exporter emits (service.name="...").

Support for target_info was added in #3073 and there is no environment variable to disable it.

[Jdsleppy]

Duplicate of #3571 and is on the way to being fixed.