I would like to be able to use a private option in
#6393 in tests,
and decided to split this refactoring out into its own PR.

This moves the batch span processor benchmarks into benchmark_test.go,
and replaces one instance of the tracetest.NewInMemoryExporter with a
different test exporter implementation. It then moves most unit tests
from `trace_test` to the main `trace` package.

This release is the last to support [Go 1.23].
The next release will require at least [Go 1.24].

### Added

- Add native histogram exemplar support in
`go.opentelemetry.io/otel/exporters/prometheus`. (#6772)
- Add template attribute functions to the
`go.opentelmetry.io/otel/semconv/v1.34.0` package. (#6939)
  - `ContainerLabel`
  - `DBOperationParameter`
  - `DBSystemParameter`
  - `HTTPRequestHeader`
  - `HTTPResponseHeader`
  - `K8SCronJobAnnotation`
  - `K8SCronJobLabel`
  - `K8SDaemonSetAnnotation`
  - `K8SDaemonSetLabel`
  - `K8SDeploymentAnnotation`
  - `K8SDeploymentLabel`
  - `K8SJobAnnotation`
  - `K8SJobLabel`
  - `K8SNamespaceAnnotation`
  - `K8SNamespaceLabel`
  - `K8SNodeAnnotation`
  - `K8SNodeLabel`
  - `K8SPodAnnotation`
  - `K8SPodLabel`
  - `K8SReplicaSetAnnotation`
  - `K8SReplicaSetLabel`
  - `K8SStatefulSetAnnotation`
  - `K8SStatefulSetLabel`
  - `ProcessEnvironmentVariable`
  - `RPCConnectRPCRequestMetadata`
  - `RPCConnectRPCResponseMetadata`
  - `RPCGRPCRequestMetadata`
  - `RPCGRPCResponseMetadata`
- Add `ErrorType` attribute helper function to the
`go.opentelmetry.io/otel/semconv/v1.34.0` package. (#6962)
- Add `WithAllowKeyDuplication` in `go.opentelemetry.io/otel/sdk/log`
which can be used to disable deduplication for log records. (#6968)
- Add `WithCardinalityLimit` option to configure the cardinality limit
in `go.opentelemetry.io/otel/sdk/metric`. (#6996, #7065, #7081, #7164,
#7165, #7179)
- Add `Clone` method to `Record` in `go.opentelemetry.io/otel/log` that
returns a copy of the record with no shared state. (#7001)
- Add experimental self-observability span and batch span processor
metrics in `go.opentelemetry.io/otel/sdk/trace`. Check the
`go.opentelemetry.io/otel/sdk/trace/internal/x` package documentation
for more information. (#7027, #6393, #7209)
- The `go.opentelemetry.io/otel/semconv/v1.36.0` package. The package
contains semantic conventions from the `v1.36.0` version of the
OpenTelemetry Semantic Conventions. See the [migration
documentation](./semconv/v1.36.0/MIGRATION.md) for information on how to
upgrade from `go.opentelemetry.io/otel/semconv/v1.34.0.`(#7032, #7041)
- Add support for configuring Prometheus name translation using
`WithTranslationStrategy` option in
`go.opentelemetry.io/otel/exporters/prometheus`. The current default
translation strategy when UTF-8 mode is enabled is
`NoUTF8EscapingWithSuffixes`, but a future release will change the
default strategy to `UnderscoreEscapingWithSuffixes` for compliance with
the specification. (#7111)
- Add experimental self-observability log metrics in
`go.opentelemetry.io/otel/sdk/log`. Check the
`go.opentelemetry.io/otel/sdk/log/internal/x` package documentation for
more information. (#7121)
- Add experimental self-observability trace exporter metrics in
`go.opentelemetry.io/otel/exporters/stdout/stdouttrace`. Check the
`go.opentelemetry.io/otel/exporters/stdout/stdouttrace/internal/x`
package documentation for more information. (#7133)
- Support testing of [Go 1.25]. (#7187)
- The `go.opentelemetry.io/otel/semconv/v1.37.0` package. The package
contains semantic conventions from the `v1.37.0` version of the
OpenTelemetry Semantic Conventions. See the [migration
documentation](./semconv/v1.37.0/MIGRATION.md) for information on how to
upgrade from `go.opentelemetry.io/otel/semconv/v1.36.0.`(#7254)

### Changed

- Optimize `TraceIDFromHex` and `SpanIDFromHex` in
`go.opentelemetry.io/otel/sdk/trace`. (#6791)
- Change `AssertEqual` in `go.opentelemetry.io/otel/log/logtest` to
accept `TestingT` in order to support benchmarks and fuzz tests. (#6908)
- Change `DefaultExemplarReservoirProviderSelector` in
`go.opentelemetry.io/otel/sdk/metric` to use `runtime.GOMAXPROCS(0)`
instead of `runtime.NumCPU()` for the `FixedSizeReservoirProvider`
default size. (#7094)

### Fixed

- `SetBody` method of `Record` in `go.opentelemetry.io/otel/sdk/log` now
deduplicates key-value collections (`log.Value` of `log.KindMap` from
`go.opentelemetry.io/otel/log`). (#7002)
- Fix `go.opentelemetry.io/otel/exporters/prometheus` to not append a
suffix if it's already present in metric name. (#7088)
- Fix the `go.opentelemetry.io/otel/exporters/stdout/stdouttrace`
self-observability component type and name. (#7195)
- Fix partial export count metric in
`go.opentelemetry.io/otel/exporters/stdout/stdouttrace`. (#7199)

### Deprecated

- Deprecate `WithoutUnits` and `WithoutCounterSuffixes` options,
preferring `WithTranslationStrategy` instead. (#7111)
- Deprecate support for `OTEL_GO_X_CARDINALITY_LIMIT` environment
variable in `go.opentelemetry.io/otel/sdk/metric`. Use
`WithCardinalityLimit` option instead. (#7166)