Improve BlobReader interface

[preston-evans98]

Description

The current BlobReaderTrait looks almost identical to std::io::Read with a few extra methods for fetching blockchain-specific data. However, there significant differences in the way that the two traits are meant to be used. While the std reader is meant to be consumed only once, our readers are meant to be consumed twice - once by the prover and once by the verifier. This makes it very easy to introduce subtle bugs, such as consuming data in the host and forgetting to "reset" the reader before passing it to the guest.

This PR changes the BlobReader API to make it more misuse resistant, and uses the new API to fix a bug in the old implementation.

Fixes #456

Testing

This change is covered by existing unit tests.

[codecov]

Codecov Report

Merging #794 (c66fc32) into nightly (777ce00) will decrease coverage by 0.1%.
The diff coverage is 70.9%.

Files Changed	Coverage Δ
adapters/celestia/src/verifier/mod.rs	0.0% <0.0%> (ø)
...ystem/sov-modules-stf-template/src/app_template.rs	89.0% <87.5%> (-0.3%)	⬇️
rollup-interface/src/state_machine/da.rs	97.2% <95.8%> (+17.6%)	⬆️
full-node/sov-sequencer/src/lib.rs	93.0% <100.0%> (-0.5%)	⬇️
rollup-interface/src/state_machine/mocks/da.rs	70.1% <100.0%> (+2.9%)	⬆️

... and 2 files with indirect coverage changes