fix: _set_keyspace_for_all_pools passes only the last pool's errors to callback #1172

Job	Run time
Test wheels building / Build source distribution	14s
Test wheels building / Prepare matrix to run for 3.13 on `linux,macos-x86,macos-arm,windows,linux-aarch64`	4s
Test wheels building / Build wheels for macos-arm on macos-14	10m 39s
Test wheels building / Build wheels for windows on windows-2022	23m 56s
Test wheels building / Build wheels for macos-x86 on macos-15-intel	35m 42s
Test wheels building / Build wheels for linux-aarch64 on ubuntu-24.04-arm	15m 59s
Test wheels building / Build wheels for linux on ubuntu-24.04	14m 43s
	1h 41m 17s

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