Providers do not check instrumentation scope attributes when returning cached loggers, tracers, or meters

[dbarker]

Describe your environment
main branch at 6ed0651

Background
After working with the otel python api/sdk a bit and reviewing the 1.40.0 OTEL spec it seems that the c++ implementation of the GetTracer, GetLogger, and GetMeter may not be fully meeting the spec with respect to these methods returning distinct instances based on all parameters including the attributes. Reading the spec I'd expect that calling GetTracer with different attributes would return different tracers but that is not the case.

Steps to reproduce
The following test illustrates the issue.

TEST(TracerProviderTest, DistinctTracers)
{    
    auto processor = opentelemetry::sdk::trace::SimpleSpanProcessorFactory::Create(std::move(opentelemetry::exporter::trace::OStreamSpanExporterFactory::Create()));
    auto provider = opentelemetry::sdk::trace::TracerProviderFactory::Create(std::move(processor));

    auto tracer_1 = provider->GetTracer("my_library", "1.0.0", "my_schema_url");
    auto tracer_2 = provider->GetTracer("my_library", "1.0.0", "my_schema_url", {{ "instance", "one" }});
    auto tracer_3 = provider->GetTracer("my_library", "1.0.0", "my_schema_url", {{ "instance", "two" }});
    
    ASSERT_NE(tracer_1, nullptr);
    ASSERT_NE(tracer_2, nullptr);
    ASSERT_NE(tracer_3, nullptr);

    EXPECT_NE(tracer_1.get(), tracer_2.get()) << "providers must return distinct tracers if there are any differences in parameters passed to GetTracer";
    EXPECT_NE(tracer_2.get(), tracer_3.get()) << "providers must check for any difference in attributes too";   
}

What is the expected behavior?
Test passes

What is the actual behavior?
Test fails

 [==========] Running 1 test from 1 test suite.
 [----------] Global test environment set-up.
 [----------] 1 test from TracerProviderTest
 [ RUN      ] TracerProviderTest.DistinctTracers
 Expected: (tracer_1) != (tracer_2), actual: 0x5995d6ce5b70 vs 0x5995d6ce5b70
 providers must return distinct tracers if there are any differences in parameters passed to GetTracer
 Expected: (tracer_2) != (tracer_3), actual: 0x5995d6ce5b70 vs 0x5995d6ce5b70
 providers must check for any difference in attributes too
 [  FAILED  ] TracerProviderTest.DistinctTracers (0 ms)
 [----------] 1 test from TracerProviderTest (0 ms total)
 [----------] Global test environment tear-down
 [==========] 1 test from 1 test suite ran. (0 ms total)
 [  PASSED  ] 0 tests.
 [  FAILED  ] 1 test, listed below:
 [  FAILED  ] TracerProviderTest.DistinctTracers

Additional context
The current 1.40.0 OTEL specification has language that seems to imply any difference in parameters passed to get_logger, get_tracer, and get_meter must result in a distinct instance.

The term identical applied to Tracers describes instances where all parameters are equal. The term distinct applied to Tracers describes instances where at least one parameter has a different value.

The term identical applied to Meters describes instances where all parameters are equal. The term distinct applied to Meters describes instances where at least one parameter has a different value.

The term identical applied to Loggers describes instances where all parameters are equal. The term distinct applied to Loggers describes instances where at least one parameter has a different value.

The InstrumentationScope::equal method doesn't account for attributes

[dbarker]

If my interpretation of the spec is correct, I'd be happy to help with a PR.