Fix: Eliminate redundant full table scans in messages and events collection

[MoralCode]

The below PR contents are lightly modified (to adjust issue and PR references mostly) from github.com/augurlabs/augur/pull/3444, filed by @PredictiveManish. The PR itself has been rebased to account for changes to CollectOSS since the fork and resolve merge conflicts

Description

Moved mapping queries outside batch loops and pass pre-built mappings as parameters to processing functions, following the pattern established by Shlok in augurlabs/augur#3439.

Changes Made

collectoss/tasks/github/messages.py

• Built issue_url_to_id_map and pr_issue_url_to_id_map once in collect_github_messages() before any batch processing
• Updated process_messages() to accept mappings as parameters instead of rebuilding them
• Updated process_large_issue_and_pr_message_collection() to accept and pass mappings
• Increased batch size from 20 to 1000 (reduces batch overhead)

collectoss/tasks/github/events.py

• Built issue_url_to_id_map and pr_url_to_id_map once in BulkGithubEventCollection.collect() before the batch loop
• Updated _process_events(), _process_issue_events(), and _process_pr_events() to accept mappings as parameters
• Removed redundant _get_map_from_*() calls from batch processing methods

Performance Improvement

• Before: 1,000 messages -> 50 full scans of issues AND PRs tables

• After: 1,000 messages -> 1 full scan of each table (50x reduction)

• Before: 10,000 events -> 40 full scans total

• After: 10,000 events → 1 full scan of each table (40x reduction)

This PR fixes #146

Notes for Reviewers

Signed commits

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