Logged errors by IPT manager with ArtiKeystoreKind::Ephemeral

I'm aware this may be due to incorrect use of something that is meant to be arti-internal (see also #1186 for context), but +gabi on #tor-dev suggested I consider filing an issue for this:

Essentially, with ArtiKeystoreKind::Ephemeral there's still IPT state going to be written, which on the 2nd start is going to cause the following errors because the state is picked up, but the keys haven't been persisted:

[2025-01-27T13:00:19Z INFO  tor_hsservice] Launching onion service nickname=ephemeral
[2025-01-27T13:00:19Z ERROR tor_hsservice::ipt_mgr] HS service ephemeral missing previous key ArtiPath("hss/ephemeral/ipts/k_hss_ntor+884cb5759264b9f073dbb8a629147d6217efb47159dc140fe96fc9463eb92921"), regenerating
[2025-01-27T13:00:19Z ERROR tor_hsservice::ipt_mgr] HS service ephemeral missing previous key ArtiPath("hss/ephemeral/ipts/k_sid+884cb5759264b9f073dbb8a629147d6217efb47159dc140fe96fc9463eb92921"), regenerating
[2025-01-27T13:00:19Z ERROR tor_hsservice::ipt_mgr] HS service ephemeral missing previous key ArtiPath("hss/ephemeral/ipts/k_hss_ntor+d3dae653a77287ceac4ac06a0c72b0accb5d73129857324529b120af647ac2d9"), regenerating
[2025-01-27T13:00:19Z ERROR tor_hsservice::ipt_mgr] HS service ephemeral missing previous key ArtiPath("hss/ephemeral/ipts/k_sid+d3dae653a77287ceac4ac06a0c72b0accb5d73129857324529b120af647ac2d9"), regenerating
[2025-01-27T13:00:19Z ERROR tor_hsservice::ipt_mgr] HS service ephemeral missing previous key ArtiPath("hss/ephemeral/ipts/k_hss_ntor+7f2637037dc86d78849ea1c5db2d763d77ce53b6ca5ba7147874ba077549243f"), regenerating
[2025-01-27T13:00:19Z ERROR tor_hsservice::ipt_mgr] HS service ephemeral missing previous key ArtiPath("hss/ephemeral/ipts/k_sid+7f2637037dc86d78849ea1c5db2d763d77ce53b6ca5ba7147874ba077549243f"), regenerating

Maybe if the keystore is ephemeral this could disable writing introduction-point state too?