Add testing for Go 1.20

[MrAlias]

Mirror of open-telemetry/opentelemetry-go#3693

[codecov]

Codecov Report

Merging #3372 (f9441ec) into main (6178903) will increase coverage by 0.0%.
The diff coverage is 80.3%.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #3372   +/-   ##
=====================================
  Coverage   69.5%   69.6%           
=====================================
  Files        147     147           
  Lines       6894    6910   +16     
=====================================
+ Hits        4796    4812   +16     
  Misses      1978    1978           
  Partials     120     120           

Impacted Files	Coverage Δ
detectors/gcp/gce.go	8.7% <0.0%> (ø)
detectors/gcp/gke.go	0.0% <0.0%> (ø)
....mongodb.org/mongo-driver/mongo/otelmongo/mongo.go	0.0% <0.0%> (ø)
detectors/aws/ecs/ecs.go	18.0% <18.1%> (ø)
...ion/google.golang.org/grpc/otelgrpc/interceptor.go	83.3% <50.0%> (ø)
instrumentation/net/http/otelhttp/handler.go	82.6% <50.0%> (ø)
detectors/aws/ec2/ec2.go	89.0% <100.0%> (ø)
detectors/aws/eks/detector.go	35.6% <100.0%> (ø)
detectors/aws/lambda/detector.go	92.8% <100.0%> (ø)
detectors/gcp/cloud-function.go	100.0% <100.0%> (ø)
... and 17 more

[MrAlias]

The beego instrumentation testing holds a handle to a temporary file on Windows systems. The testing system is therefore not able to cleanly close the file handle. This updates that test to use a mock filesystem instead.