* initial
* update
* fix: add validator to NewBlockchain function calls
* handle past chain reorg
* fix: only check with last checkpoint
* rm logs
* add: handle future chain import case
* fix: handle single block case
* add unit tests for past and future chain
* modularise forker tests
* minor fixes
* add: overlapping chain test case, minor fixes
* minor fixes
* add: isolated unit test for IsValidChain
* add more test case for IsValidChain
* fix: use index for header time
* add: fetch last N checkpoints in first run
* fix: change checkpoint count to int64
* fix: handle edge case
* fix: handle no checkpoint case separately
* fix: consider offset for future chain calculation
* re-write test case for split chain
* fix: typo
* add: split chain properties test
* separate reorg checks, validate chain before inserting
* fix: handle err incase of invalid chain
* fix: use error from whitelist service
* split chain property tests
* remove duplicate test cases
* cleanup
* clean up
* fix linters
* fix: fetch checkpoint count bug, add tests
* fix more linters
* fix: handle nil chain validator in downloader
* fix: mock bor tests
Co-authored-by: Evgeny Danienko <6655321@bk.ru>
