Split token instance fetcher

[nikitosing]

Close #7024

Changelog

Now 3 fetchers are responsible for fetching token instances:

• Realtime fetcher:
  • processes token transfers which are not in token_instances table came from Block.Fetchers
  • if token instance fetch successed then token instance added to token_instances table. If not then also added but with some error
• Retry fetcher:
  • continiously refetches token instances: SELECT * FROM token_instances WHERE error IS NOT NULL
  • if token instance fetch successed then token instance updated. If not then do nothing
• Sanitize fetcher:
  • once and just after starting the server this fetcher process all the token instances which are not in token_instances table
  • if token instance fetch successed then token instance added to token_instances table. If not then also added but with some error

Remove:

• INDEXER_TOKEN_INSTANCE_BATCH_SIZE
• INDEXER_TOKEN_INSTANCE_CONCURRENCY

Add:

• INDEXER_TOKEN_INSTANCE_RETRY_REFETCH_INTERVAL
• INDEXER_TOKEN_INSTANCE_RETRY_CONCURRENCY
• INDEXER_TOKEN_INSTANCE_REALTIME_CONCURRENCY
• INDEXER_TOKEN_INSTANCE_SANITIZE_CONCURRENCY

blockscout/docs#141

Checklist for your Pull Request (PR)

• I added an entry to CHANGELOG.md with this PR
• If I added new functionality, I added tests covering it.
• If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.
• I checked whether I should update the docs and did so by submitting a PR to https://github.com/blockscout/docs
• If I added/changed/removed ENV var, I submitted a PR to https://github.com/blockscout/docs to update the list of env vars at https://github.com/blockscout/docs/blob/master/for-developers/information-and-settings/env-variables.md and I updated the version to master in the Version column. Changes will be reflected in this table: https://docs.blockscout.com/for-developers/information-and-settings/env-variables.
• If I add new indices into DB, I checked, that they are not redundant with PGHero or other tools

[vbaranov]

I would suggest changing the folders structure and naming of new fetcher's for consistency and reading convenience purposes. Here is the suggestion how to rename new fetchers:

Indexer.Fetcher.Realtime.TokenInstance -> Indexer.Fetcher.TokenInstance.Realtime
Indexer.Fetcher.Retry.TokenInstance -> Indexer.Fetcher.TokenInstance.Retry
Indexer.Fetcher.Sanitize.TokenInstance -> Indexer.Fetcher.TokenInstance.Sanitize
Indexer.Fetcher.TokenInstance -> Indexer.Fetcher.TokenInstance.Helper

And the folder structure like this:
apps/indexer/lib/indexer/fetcher/token_instance:
- realtime.ex
- retry.ex
- sanitize.ex
- helper.ex