don't copy union and intersection properties into the augmented property cache

[Max Schwenk (maschwenk)]

getUnionOrIntersectionProperty keeps two caches per union/intersection type, one with and one without the function property augment. when a lookup without the augment creates a property that isn't partial, it also copies it into the augmented cache. the copy is only ever read by a later augmented lookup of the same name, which can read it from the other cache instead. also, ast.GetSymbolTable allocates a cache map on the first lookup, even when nothing ever gets stored

this reads the non-augmented cache on an augmented miss (non-partial entries only, like the copy) and allocates a cache on its first store. lookups return the same symbol in any order:

• augmented property created first, non-augmented later: the augmented cache has it and is checked first. the copy didn't happen before either (it only went into an empty slot)
• non-augmented property created first: before, the augmented lookup found the copy, now it finds the same symbol in the other cache
• partial properties: never copied before, never read from the other cache now, so the augmented lookup still creates its own

nothing else reads these caches

on our 38k-file program (37,943 files, 0 errors), median of 3, one process at a time:

	heap after check	allocs
main, single threaded	14.03 GB → 13.84 GB (−1.4%)	148.86M → 147.86M (−1.0M)
main, 4 checkers	21.25 GB → 20.96 GB (−1.4%)	246.89M → 245.02M (−1.9M)
main + #64475 + #64526 + 3 unopened follow ups, single threaded	10.36 GB → 10.23 GB (−1.3%)	149.24M → 148.42M (−0.8M)
main + #64475 + #64526 + 3 unopened follow ups, 4 checkers	15.07 GB → 14.84 GB (−1.5%)	248.70M → 247.09M (−1.6M)

symbols, types and instantiations don't change (25,972,751 / 9,639,290 / 44,879,960 on main single threaded). heap is Memory used from --extendedDiagnostics (live heap after GC; spreads by under 0.01 GB between runs single threaded, up to 0.15 GB with 4 checkers), allocs is Memory allocs. check time is within noise

per path (counted in an instrumented port of the checker with the same change, on that stack): 2.37M fewer cache entries single threaded (3.39M with 4 checkers), and 70,673 augmented lookups are served from the other cache

same diagnostics on every run. go test ./... passes (except the macOS fsevents tests in internal/fswatch, which time out here under load and pass on a rerun), the testrunner also with TS_TEST_PROGRAM_SINGLE_THREADED=false, lint and format are clean. no new test, the change has no observable effect besides memory

used claude code to help write this, ive reviewed it

[Max Schwenk (maschwenk)]

Withdrawing this one: the gain is too small to be worth reviewer time on its own. The larger change is #64475 / #64526.