[cli] Add command to generate index/bloom from a data file

[annanay25]

What this PR does:

• Adds a command to generate the index from a data file. To test, run:

go run ./cmd/tempo-cli gen index --backend=local --bucket=./cmd/tempo-cli/test-data/ single-tenant b18beca6-4d7f-4464-9f72-f343e688a4a0

The new index file will be created in the test-data/single-tenant/b18beca6-4d7f-4464-9f72-f343e688a4a0 folder.

Diff the newly generated index with the index-copy present in the same folder. There should be no differences.

• This PR also adds some diagrams that help with understanding the encoding package. The drawio XML file is also included. The expectation is that the xml and png file will be version controlled but it is not on the official website docs and so it doesn't have to be updated with every PR.

Which issue(s) this PR fixes:
Fixes #894

Checklist

• Tests updated
  • Needs some form of runtime validation as well
• Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

Signed-off-by: Annanay annanayagarwal@gmail.com

[annanay25]

Added a very basic index verifier and I think the first stage of should include just the local backend. As follow ups, we can implement a remote backend reader which will involve implementing an io.Reader for the S3 backend.

[joe-elliott]

Also, let's improve these docs:

https://github.com/grafana/tempo/blob/main/docs/tempo/website/troubleshooting/bad-blocks.md

now that your PR adds a way to fix blocks!