[wallet] {dump,import}wallet incompatible with HD #8308

I am assuming dumpwallet and importwallet no longer work when -usehd is set. This should be mentioned somewhere because it may not be obvious.

Apparently there is already something ready for review: #8206

That's a good point.

importwallet could somewhat-work, I don't think the hd wallet forbids importing keys?

importwallet works in conjunction with HD and IMO it does exactly what it should (importing a wallet/keys but not importing the hd seed not activating the hdseed). The later could be discussed.

One could "import" multiple wallets and I think re-activatig the HD seed would be wrong in this case.

Edit: "it does import the seed but it does not activate it"

One could "import" multiple wallets and I think re-activatig the HD seed would be wrong in this case.

I feel like it should be at least documented that HD-seeds are not activated. This may not be obvious to everyone.

Something nice to have for 0.14: Warn when importwallet finds a HD seed, because it can not be activated in neither case. Having your current wallet be a legacy wallet, it would be not intuitive to suddenly switch to a HD wallet; And having your current wallet be a HD wallet, you can not import another HD seed...

We could also just write the HD seed to the dump...

We could also just write the HD seed to the dump...

#8206 does that.