[Unit Tests] Fix lag after Unit Tests finish, fix flakiness in Sampling test (aws-observability#78)

*Issue #, if available:*
- `npm run test` command stalls for 20s after all tests pass (or fail),
discovered caused by `Concurrency` test, likely due to
`exportTimeoutMillis` default value being set in
`AwsBatchUnsampledSpanProcessor`
- Flaky test case `testSomeReservoir` that may fail when sampling
targets are not refreshed in time for the unit tests (due to the test
being reliant on `setTimeout` which doesn't guarantee exact time of
execution).
-
https://github.com/aws-observability/aws-otel-js-instrumentation/actions/runs/11023689994/job/30615442620#step:7:560

*Description of changes:*
- Add short `exportTimeoutMillis` value for
`AwsBatchUnsampledSpanProcessor` config in `Concurrency` test
- Update `testSomeReservoir` to properly cleanup the fake clock, provide
more time for Sampling targets to refresh on time for the unit test run.

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Author: jj22ee

aws-distro-opentelemetry-node-autoinstrumentation/test/aws-batch-unsampled-span-processor.test.ts

@@ -457,6 +457,7 @@ describe('AwsBatchUnsampledSpanProcessor', () => {
       const processor = new AwsBatchUnsampledSpanProcessor(exporter, {
         maxExportBatchSize: 5,
         maxQueueSize: 6,
+        exportTimeoutMillis: 1000,
       });
       const totalSpans = 50;
       for (let i = 0; i < totalSpans; i++) {

aws-distro-opentelemetry-node-autoinstrumentation/test/sampler/aws-xray-remote-sampler.test.ts

@@ -88,6 +88,9 @@ describe('AwsXrayRemoteSampler', () => {
       ).toEqual(SamplingDecision.NOT_RECORD);
 
       setTimeout(() => {
+        // restore function
+        (_AwsXRayRemoteSampler.prototype as any).getDefaultTargetPollingInterval = tmp;
+
         expect(
           sampler.shouldSample(context.active(), '1234', 'name', SpanKind.CLIENT, { abc: '1234' }, []).decision
         ).toEqual(SamplingDecision.RECORD_AND_SAMPLED);
@@ -98,8 +101,6 @@ describe('AwsXrayRemoteSampler', () => {
           sampler.shouldSample(context.active(), '1234', 'name', SpanKind.CLIENT, { abc: '1234' }, []).decision
         ).toEqual(SamplingDecision.RECORD_AND_SAMPLED);
 
-        // reset function
-        (_AwsXRayRemoteSampler.prototype as any).getDefaultTargetPollingInterval = tmp;
         done();
       }, 300);
     }, 10);
@@ -139,10 +140,12 @@ describe('AwsXrayRemoteSampler', () => {
             sampled++;
           }
         }
+
+        // restore function
+        (_AwsXRayRemoteSampler.prototype as any).getDefaultTargetPollingInterval = tmp;
+
         expect((sampler as any)._root._root.ruleCache.ruleAppliers[0].reservoirSampler.quota).toEqual(100000);
         expect(sampled).toEqual(100000);
-        // reset function
-        (_AwsXRayRemoteSampler.prototype as any).getDefaultTargetPollingInterval = tmp;
         done();
       }, 2000);
     }, 100);
@@ -184,13 +187,13 @@ describe('AwsXrayRemoteSampler', () => {
             sampled++;
           }
         }
-        expect(sampled).toEqual(100);
-        // reset function
-        (_AwsXRayRemoteSampler.prototype as any).getDefaultTargetPollingInterval = tmp;
         clock.restore();
+        // restore function
+        (_AwsXRayRemoteSampler.prototype as any).getDefaultTargetPollingInterval = tmp;
+        expect(sampled).toEqual(100);
         done();
       }, 2000);
-    }, 100);
+    }, 300);
   });
 
   it('generates valid ClientId', () => {