debuginfo: NewDebugInfodClientWithObjectStorageCache never reads back from bucket

[kakkoyun]

We write to the bucket, however, we never read back. This cause probably multiple downloads to the bucket. https://github.com/parca-dev/parca/blob/12949775f8d7def1ce24fe44198b482c80aa507c/pkg/debuginfo/debuginfod.go#L88-L91

Moreover, we don't have any synchronization mechanism around this. I propose we upload directly to the debuginfo object store using metadata locking facilities.

[brancz]

Whops nice catch. Yeah, I agree we should use the same synchronization techniques, and maybe more importantly, actually read from object storage if we have the debuginfos there already :D

[brancz]

(sorry mistakenly closed the issue, reopened immediately)