capi: fork validator fixes

[JacekGlen]

The changes in this PR stem from testing tip execution in Erigon++. I tried to add unit test coverage, but some tests are difficult to setup. In any case Erigon has Silkworm CAPI tests that covers these scenarios.
Changes:

• standardize the use of etl_mdbx::Collector - the pointer points to an object created on a function call and is deleted before the function returns
• HashState::get_log_progress() is more resilient and can be called at any time
• unify constructor setup for stages - delete copy and move constructors
• access_layer can be called on the genesis block