Specify whether bootstrap pull should start at block hash or account

[pwojcikdev]

There are accounts with the same hash as another block in our live ledger. That creates ambiguity and makes it impossible to pull those account chains. This PR removes that ambiguity by always specifying whether requested hash is a block or account.

[clemahieu]

Is this something that would be better as a header flag?

[dsiganos]

I do not agree with creating an enum for something that has only 2 states.
I would prefer to see a flag used. But other than that, looks good to me.

[pwojcikdev]

@dsiganos I don't understand how enum conflicts with using flags? IMHO it's much better code style to define you flags as an enum (in contrast to defining const ints, C style). One of the first links I found on the internet you might want to check out, specifically the section on std::bitset https://m-peko.github.io/craft-cpp/posts/different-ways-to-define-binary-flags/

[dsiganos]

@pwojcikdev This is mostly stylistic disagreement so no big deal if we go one way or another.
I come from a traditional C background so uint8 with masks, seems perfectly natural to me.
For me, the fact that the enum has more than 2 states causes an unwanted complication.
But, this is just a stylistic disagreement, so it doesn't really matter.