Identify and implement top five code reduction

Identify top 5 opportunities to massively reduce the amount of code (lines of code) in any part of the repo: - Similar functionality that can be unified and reused - Code that has been valuable but no more - A front end component or a group of them duplicate another component/page functionality. Use the most modern and nice looking - etc. Now implement them :)

Top-five code reduction: one externalStore helper behind 11 web stores, dead symbols deleted, 7 UTC-stamp copies single-homed, 57 flagged tests triaged (0 deletable, 1 repaired); legacy-compat pools deferred (fleet floor). Net −181 prod lines. Quick gate green, review+verify PASS. PR #7080 queued in the merge lane. Side fix: test_transfer_rules.py now gated. Memory: used mem-25288; proposed none.