feat: blob sliver data existence check

[halfprice]

Description

This PR implements the basic sliver data existence check conducted along with blob info consistency check
at beginning of every epoch. It exposes a metric which represents the percentage of fully synced blobs that
are actually fully stored. Note that here it has already taken blobs that are being synced into consideration.

Contribute to WAL-701

Test plan

How did you test the new or updated feature?

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Release notes

Check each box that your changes affect. If none of the boxes relate to your changes, release notes aren't required.
For each box you select, include information after the relevant heading that describes the impact of your changes that
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• Storage node:
• Aggregator:
• Publisher:
• CLI:

[github-actions]

Warning: This PR modifies one of the example config files. Please consider the
following:

• Make sure the changes are backwards compatible with the current configuration.
• Make sure any added parameters follow the conventions of the existing parameters; in
  particular, durations should take seconds or milliseconds using the naming convention
  _secs or _millis, respectively.
• If there are added optional parameter sections, it should be possible to specify them
  partially. A useful pattern there is to implement Default for the struct and derive
  #[serde(default)] on it, see BlobRecoveryConfig as an example.
• You may need to update the documentation to reflect the changes.

[sadhansood]

I think this looks good to me, i hope @liquid-helium can also once take a look and ensure his comments are fully addressed.

[liquid-helium]

This looks good to me, I left some comments but we don't need to resolve them in this PR.