HPCC-35522 Refactor blob reading to use cache and readahead

[ghalliday]

Type of change:

• This change is a bug fix (non-breaking change which fixes an issue).
• This change is a new feature (non-breaking change which adds functionality).
• This change improves the code (refactor or other change that does not change the functionality)
• This change fixes warnings (the fix does not alter the functionality or the generated code)
• This change is a breaking change (fix or feature that will cause existing behavior to change).
• This change alters the query API (existing queries will have to be recompiled)

Checklist:

• My code follows the code style of this project.
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  • Existing deployed queries will not be broken
  • This change fixes the problem, not just the symptom
  • The target branch of this pull request is appropriate for such a change.
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  • I have addressed them here
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Testing:

[Copilot]

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[github-actions]

Jira Issue: https://hpccsystems.atlassian.net//browse/HPCC-35522

Jirabot Action Result:
Assigning user: gavin.halliday@lexisnexisrisk.com
Workflow Transition To: Merge Pending
Updated PR

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

[mckellyln]

Looks good, just had one question/comment.

[mckellyln]

Approved.

[github-actions]

Jirabot Action Result:
Added fix version: 10.0.22
Workflow Transition: 'Resolve issue'