Unify aws lambda flush handling

[laurit]

Supersedes #12375
Set default flush timeout for agent instrumentation to 10s as it is for the wrapper used in the library configuration.

[laurit]

As far as I can tell this is configured in

opentelemetry-java-instrumentation/instrumentation/aws-lambda/aws-lambda-core-1.0/library/src/main/java/io/opentelemetry/instrumentation/awslambdacore/v1_0/internal/WrapperConfiguration.java

Lines 20 to 32 in 78b3c6a

	public static final Duration OTEL_LAMBDA_FLUSH_TIMEOUT_DEFAULT = Duration.ofSeconds(10);
	public static Duration flushTimeout() {
	String lambdaFlushTimeout = System.getenv(OTEL_LAMBDA_FLUSH_TIMEOUT_ENV_KEY);
	if (lambdaFlushTimeout != null && !lambdaFlushTimeout.isEmpty()) {
	try {
	return Duration.ofMillis(Long.parseLong(lambdaFlushTimeout));
	} catch (NumberFormatException nfe) {
	// ignored - default used
	}
	}
	return OTEL_LAMBDA_FLUSH_TIMEOUT_DEFAULT;
	}

[steverao]

How about using Long instead of Integer here? in java.util.concurrent.TimeUnit, I noticed it used long type for millisecond or other unit of time.

[laurit]

Does it really matter? From user perspective I'd assume it is only important to know that a numeric value is expected.

[trask]

for configuration, I think we only need to specify something like "int" or "double", similar to semantic convention attribute types

[trask]

maybe keep and mark the int variant deprecated for removal in 3.0? seems like something that could be in use by an extension

[laurit]

I added back the original method. If the indy extension changes get done in time for 3.0 it is possible that we won't need most of the bootstrap classes any more.