Improve perf of blob retrieval within bucket

[jianoaix]

Why are these changes needed?

This is perf optimization for blob feed retrieval:

• Apply limit to within bucket retrieval
  • e.g. if the client wants just 1 blob, it won't need to exhaust the entire bucket (which can have up to 360,000 blobs, assuming 100 blobs/ and 1h per bucket)
• Avoid allocating additional slice

Checks

• I've made sure the tests are passing. Note that there might be a few flaky tests, in that case, please comment that they are not relevant.
• I've checked the new test coverage and the coverage percentage didn't drop.
• Testing Strategy
  • Unit tests
  • Integration tests
  • This PR is not tested :(