Refactor exporter - step 9

[reyang]

This is a follow up PR of #1078.

Changes

Just renaming:

• s/ActivityExporterSync/ActivityExporter/g
• s/ExportResultSync/ExportResult/g

For significant contributions please make sure you have completed the following items:

• Design discussion issue #
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #1129 into master will not change coverage.
The diff coverage is 37.50%.

@@           Coverage Diff           @@
##           master    #1129   +/-   ##
=======================================
  Coverage   77.33%   77.33%           
=======================================
  Files         220      220           
  Lines        6256     6256           
=======================================
  Hits         4838     4838           
  Misses       1418     1418           

Impacted Files	Coverage Δ
...rc/OpenTelemetry.Exporter.Jaeger/JaegerExporter.cs	69.76% <0.00%> (ø)
...try.Exporter.OpenTelemetryProtocol/OtlpExporter.cs	29.41% <0.00%> (ø)
...rc/OpenTelemetry.Exporter.ZPages/ZPagesExporter.cs	90.90% <0.00%> (ø)
...nTelemetry/Internal/OpenTelemetrySdkEventSource.cs	80.95% <ø> (ø)
src/OpenTelemetry/Trace/ActivityExporter.cs	80.00% <ø> (ø)
...enTelemetry/Trace/SimpleExportActivityProcessor.cs	100.00% <ø> (ø)
...rc/OpenTelemetry.Exporter.Zipkin/ZipkinExporter.cs	86.84% <50.00%> (ø)
...penTelemetry/Trace/BatchExportActivityProcessor.cs	36.36% <100.00%> (ø)
...elemetry/Trace/ReentrantExportActivityProcessor.cs	27.27% <100.00%> (ø)
...ZPages/Implementation/ZPagesExporterEventSource.cs	56.25% <0.00%> (-6.25%)	⬇️
... and 1 more