Move log.Processor.Enabled to independent FilterProcessor interfaced type (#5692)

Closes #5425 

Our current log `Processor` interface contains more functionality than
the [OTel
spec](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/logs/sdk.md#logrecordprocessor-operations).
The additional functionality allows processors to report back to the API
if a Record should be constructed and emitted or not, which is quite
helpful[^1][^2][^3][^4][^5].

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

```terminal
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.

[^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]:
af75717ac4/bridges/otelslog/handler.go (L206-L211)
[^5]:
d0309ddd8c/bridges/otelzap/core.go (L142-L146)

---------

Co-authored-by: Robert Pająk <pellared@hotmail.com>
Co-authored-by: Sam Xie <sam@samxie.me>

sdk/log/simple_test.go

@@ -52,12 +52,6 @@ func TestSimpleProcessorOnEmit(t *testing.T) {
 	assert.Equal(t, []log.Record{*r}, e.records)
 }
 
-func TestSimpleProcessorEnabled(t *testing.T) {
-	e := new(exporter)
-	s := log.NewSimpleProcessor(e)
-	assert.True(t, s.Enabled(context.Background(), log.Record{}))
-}
-
 func TestSimpleProcessorShutdown(t *testing.T) {
 	e := new(exporter)
 	s := log.NewSimpleProcessor(e)
@@ -97,7 +91,6 @@ func TestSimpleProcessorEmpty(t *testing.T) {
 		ctx := context.Background()
 		record := new(log.Record)
 		assert.NoError(t, s.OnEmit(ctx, record), "OnEmit")
-		assert.False(t, s.Enabled(ctx, *record), "Enabled")
 		assert.NoError(t, s.ForceFlush(ctx), "ForceFlush")
 		assert.NoError(t, s.Shutdown(ctx), "Shutdown")
 	})
@@ -119,7 +112,6 @@ func TestSimpleProcessorConcurrentSafe(t *testing.T) {
 			defer wg.Done()
 
 			_ = s.OnEmit(ctx, r)
-			_ = s.Enabled(ctx, *r)
 			_ = s.Shutdown(ctx)
 			_ = s.ForceFlush(ctx)
 		}()