Move log.Processor.Enabled to independent FilterProcessor interfaced type

[MrAlias]

Closes #5425

Our current log Processor interface contains more functionality than the OTel spec. The additional functionality allows processors to report back to the API if a Record should be constructed and emitted or not, which is quite helpful¹²³⁴⁵.

This removes the Enabled method from the Processor type. It adds this functionality a new optional and experimental FilterProcessor interface type. The logger and provider are updated to check for this optional interface to be implemented with the configured processors and uses them to back the Logger.Enabled method, preserving existing functionality.

By making this change:

• The Processor interface is now compliant with the OTel spec and does not contain any additional unspecified behavior.
• All Processor implementations are no longer required to implement an Enabled method. The default, when they do not implement this method, is to assume they are enabled.

Benchmark

goos: linux
goarch: amd64
pkg: go.opentelemetry.io/otel/sdk/log
cpu: Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz
                │   old.txt    │              new7.txt               │
                │    sec/op    │   sec/op     vs base                │
LoggerEnabled-8   133.30n ± 3%   32.36n ± 3%  -75.72% (p=0.000 n=10)

                │  old.txt   │            new7.txt            │
                │    B/op    │    B/op     vs base            │
LoggerEnabled-8   0.000 ± 0%   0.000 ± 0%  ~ (p=1.000 n=10) ¹
¹ all samples are equal

                │  old.txt   │            new7.txt            │
                │ allocs/op  │ allocs/op   vs base            │
LoggerEnabled-8   0.000 ± 0%   0.000 ± 0%  ~ (p=1.000 n=10) ¹
¹ all samples are equal

This is a significant performance improvement due to the Record no longer being converted from the API version to the SDK version.

Footnotes

1. https://pkg.go.dev/go.opentelemetry.io/contrib/processors/minsev ↩

2. https://pkg.go.dev/go.opentelemetry.io/otel/sdk/log#BatchProcessor.Enabled ↩

3. https://pkg.go.dev/go.opentelemetry.io/otel/sdk/log#SimpleProcessor.Enabled ↩

4. https://github.com/open-telemetry/opentelemetry-go-contrib/blob/af75717ac4fb3ba13eaea83b88301723122060cf/bridges/otelslog/handler.go#L206-L211 ↩

5. https://github.com/open-telemetry/opentelemetry-go-contrib/blob/d0309ddd8c5714af1cd9dbe8b39b7e8f10485679/bridges/otelzap/core.go#L142-L146 ↩

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.5%. Comparing base (fe6c67e) to head (ec06ff8).
Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #5692   +/-   ##
=====================================
  Coverage   84.5%   84.5%           
=====================================
  Files        272     272           
  Lines      22634   22644   +10     
=====================================
+ Hits       19137   19148   +11     
+ Misses      3159    3158    -1     
  Partials     338     338           

see 6 files with indirect coverage changes

[XSAM]

👍

[dashpole]

lgtm after comment is addressed