Remove reversible db

[heifner]

Change Description

• Remove reversible chainbase database and use fork database instead. This optimizes block production and simplifies maintenance and recovery.
• The reversible database was storing redundant information that is available from the fork database.
• eosio-blocklog util updated to report blocks from fork database.
• The first start of nodeos from a previous version will move the fork_db.dat file from the state directory to the blocks/reversible directory.

Change Type

Select ONE:

• Documentation

• Stability bug fix

• Other

• Other - special case

Testing Changes

Select ANY that apply:

• New Tests

• Existing Tests

• Test Framework

• CI System

• Other

Consensus Changes

• Consensus Changes

API Changes

• API Changes

• /v1/db_size/get_reversible of db_size_api_plugin still exists but returns 0 for all values.

Documentation Additions

• Documentation Additions

• See API changes above.

The following options are deprecated. They are completely ignored as reversible blocks db is no longer needed.

• reversible-blocks-db-size-mb
  (DEPRECATED: no longer used) Maximum size (in MiB) of the reversible blocks database

• reversible-blocks-db-guard-size-mb
  (DEPRECATED: no longer used) Safely shut down node when free space remaining in the reverseible blocks database drops below this size (in MiB).

The following options where removed:

• --fix-reversible-blocks
• --import-reversible-blocks
• --export-reversible-blocks

The fork_db.dat file is a portable format so it can simply be copied from one installation to another without a need to export/import.