Ensure batch span processors are shutdown in examples

[dashpole]

Issue #1197.

Spans in examples are not printed out because the program finishes before spans are handled in the batch processor. Based on the API, this should be properly solved by calling Shutdown() on the batch span processor before the program terminates. I limited this change to only fixing the examples, although I think some follow-up changes are probably warranted, which I have documented in the issue.

[codecov]

Codecov Report

Merging #1199 into master will decrease coverage by 0.0%.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           master   #1199     +/-   ##
========================================
- Coverage    76.4%   76.3%   -0.1%     
========================================
  Files         134     134             
  Lines        5732    5720     -12     
========================================
- Hits         4382    4370     -12     
  Misses       1106    1106             
  Partials      244     244             

Impacted Files	Coverage Δ
sdk/trace/provider.go	92.9% <0.0%> (-3.5%)	⬇️
sdk/trace/batch_span_processor.go	80.6% <0.0%> (+2.1%)	⬆️

[Aneurysm9]

diff --git a/example/basic/main.go b/example/basic/main.go
index 21a8fa6..ab831f9 100644
--- a/example/basic/main.go
+++ b/example/basic/main.go
@@ -48,7 +48,7 @@ func main() {
 
        bsp := sdktrace.NewBatchSpanProcessor(exporter)
        defer bsp.Shutdown()
-       tp := sdktrace.NewProvider(sdktrace.WithSpanProcessor(bsp))
+       tp := sdktrace.NewTracerProvider(sdktrace.WithSpanProcessor(bsp))
        pusher := push.New(
                basic.New(
                        simple.NewWithExactDistribution(),
@@ -59,7 +59,7 @@ func main() {
        pusher.Start()
        defer pusher.Stop()
        global.SetTracerProvider(tp)
-       global.SetMeterProvider(pusher.Provider())
+       global.SetMeterProvider(pusher.MeterProvider())
 
        tracer := global.Tracer("ex.com/basic")
        meter := global.Meter("ex.com/basic")