[3.6] CP: don't clear domain RAM under a published SharedDomains (#23046) - #23164

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Fixes the high-severity finding from the #22987 review.

**Problem.** RPC read views keep a `DomainReader` pointing at the
published SD's in-memory domain maps. The background-commit teardown
(`bgSD.Close()` → `mem.Close()` → `ClearRam()`) emptied those maps while
readers were still using them. A receipt read of the in-flight block
then missed silently, fell back to the request's pre-commit tx, and
`ReceiptAsOf` zero-filled the miss: `GetReceiptsGasUsed` returned
`GasUsed=0` for every tx of the head block, and `eth_feeHistory` reward
percentiles were silently wrong. Latest-state reads could likewise fall
back to the previous block's state mid-request.

**Fix.** `TemporalMemBatch.Close` no longer clears the in-memory domain
maps: they go to the GC once the last reference drops. With that,
`ClearRam` had no production caller left and is removed entirely — the
batch has a single lifetime (write, maybe publish, close-and-drop) and
no API can clear the maps under readers. The one internal test that used
clear-and-reuse now mirrors what `cmd/integration` actually does today:
a fresh `SharedDomains` per batch.

**Tests.** New `TestClose_KeepsDomainRamForReaders` (red before the fix,
green after). One existing assert updated: a post-teardown view now
keeps serving the published head instead of falling back to its own tx.

#22987 (draft) depends on this PR: pinning the overlay across `Fork`
makes this window easier to hit, so that PR stays a draft until this one
is merged.