Support 12-word (128 bit) BIP39 mnemonic strings

[LeChatNoir69]

"entropy" parameter has been added to "karlsenwallet create" function to allow 12-words or 24-words phrase (default : 24-words).

[lemois-1337]

@LeChatNoir69 Many thanks for this pull request. Could you also extend the tests for it so that they test 128 and 256 bits?

cmd/karlsenwallet/libkaspawallet/transaction_test.go
cmd/karlsenwallet/daemon/server/split_transaction_test.go

There are still a lot of tests broken and we will fix them in near future, but lets fix it already for newly introduced features.

[LeChatNoir69]

If no arg are passed to the function, it considers 256 bits by default. I'm ok to update tests functions but not sure from where theses functions must get the right length ?

[lemois-1337]

There should be 3 tests then:

1. enforced with argument of 256 bits and check that result is correct.
2. enforced with argument of 128 bits and check that result is correct.
3. original test without argument, but ensure that the result always complies to 256 bit.

Imagine the case someone accidentally change the default from 256 to 128 with a pull request. The autotest - once the GitHub workflows are updated - will immediately fail and no manual test is needed.