ref: Move span processor out of integrations/opentelemetry/

[sentrivana]

Moving stuff out of integrations/opentelemetry/ step by step since there is no OpenTelemetry integration anymore -- it's part of the core SDK.

This moves sentry_sdk/integrations/opentelemetry/span_processor.py -> sentry_sdk/opentelemetry/span_processor.py

Ref #3853

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
20480	1	20479	4416

View the top 1 failed test(s) by shortest run time

tests.test_basics test_classmethod_tracing

Stack Traces | 0.159s run time

tests/test_basics.py:811: in test_classmethod_tracing
    assert fake_start_child.call_count == 1
E   AssertionError: assert 3 == 1
E    +  where 3 = <MagicMock name='mock.start_child' id='140335641854352'>.call_count

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[szokeasaurusrex]

nice!