Update Codecov Uploader

[Eric-Warehime]

The old codecov uploaders (including the bash script we are currently using) are now deprecated
see https://docs.codecov.com/docs/about-the-codecov-bash-uploader and https://about.codecov.io/blog/codecov-uploader-deprecation-plan/ and https://github.com/codecov/codecov-bash

We need to update our codecov upload in our CI to use the new uploader https://about.codecov.io/blog/introducing-codecovs-new-uploader/

[onetechnical]

See also: algorand/indexer#995

[onetechnical]

This was done in #3997

[cce]

This was not done in #3997 — I see in algorand/indexer#995 that it switches to using the official CircleCI orb from Codecov, but #3997 just adds a .codecov.yml config file.