Prometheus exporter should handle metric label key collisions

As described in the spec

Metrics from OpenTelemetry with unsupported Attribute names MUST replace invalid characters with the _ character. Multiple consecutive _ characters MUST be replaced with a single _ character. This may cause ambiguity in scenarios where multiple similar-named attributes share invalid characters at the same location. In such unlikely cases, if multiple key-value pairs are converted to have the same Prometheus key, the values MUST be concatenated together, separated by ;, and ordered by the lexicographical order of the original keys.

Right now this is not happening. The following code

counter = meter_provider.get_meter("scope").create_counter(
    "test_with_collision"
)
counter.add(1, {"hello_world": "hello_world", "hello.world": "hello.world"})

expected

# HELP test_with_collision_total 
# TYPE test_with_collision_total counter
test_with_collision_total{hello_world="hello.world;hello_world"} 1.0

actual

# HELP test_with_collision_total My description
# TYPE test_with_collision_total counter
test_with_collision_total{hello_world="hello_world"} 1.0

Start with the Prometheus exporter path that converts metric attribute names, then reproduce the collision using the counter example in the issue. Done means colliding keys produce one label whose values are concatenated with ; in lexicographical order, matching the expected output.