Enable Codecov again

[kzys]

We have lost Codecov since #101. While the main containerd repository
doesn't have that, ttrpc could have Codecov without much complications.

Signed-off-by: Kazuyoshi Kato katokazu@amazon.com

[codecov-commenter]

Codecov Report

Merging #105 (79bcb78) into main (d2d6bb6) will decrease coverage by 9.12%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #105      +/-   ##
==========================================
- Coverage   72.80%   63.67%   -9.13%     
==========================================
  Files          11       11              
  Lines         728     1049     +321     
==========================================
+ Hits          530      668     +138     
- Misses        156      336     +180     
- Partials       42       45       +3     

Impacted Files	Coverage Δ
client.go
codec.go
handshake.go
interceptor.go
services.go
unixcreds_linux.go
server.go
metadata.go
channel.go
config.go
... and 11 more

---

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[dmcgowan]

The inaccurate comment kind of highlights why we got rid of it in the first place. Are we using it wrong? If it just consistently adds meaningless comments with numbers that don't indicate anything, we shouldn't reenable. If we just need to fix some configuration and it will actually work, then sure.

[kzys]

We haven't sent information to Codecov for roughly a month. Having outdated information on their end (hence reporting the drop) makes some sense.

I'd like to give it a try. If it still fluctuates for a few months, we can remove the action.

[dmcgowan]

we'll see 😉