Enhancements:

• Support read-only file system #1945.
• Reduce netty pool size #1944.
• Do not apply sampling to metrics #1902.
• Add support for multiple instrumentation keys #1938.

Bug Fixes:

• Fix instrumentation key is null when sending persisted files from disk #1948.
• Fix consumer span exporter mapping #1952.
• Fix weird folder name like test%20-test #1946.