[1.0-beta4 -> main] Add max-reversible-blocks option

[heifner]

New chain_plugin option max-reversible-blocks. Specifies the maximum number of reversible blocks beyond current LIB to allow before the node is gracefully shutdown. The graceful shutdown is provided as a way to prevent out of memory kill by OS. Once consensus is working again the node can be started with a larger max-reversible-blocks value to continue.

  --max-reversible-blocks arg (=3600)   Approximate maximum allowed reversible
                                        blocks before shutdown. Will shut down
                                        if limit reached. Specify 0 to disable.

Merges release/1.0-beta4 into main including #493

Resolves #447

[ericpassmore]

Note:start
group: PROTOCOL
category: HTTP
summary: Adds new chain_plugin option max-reversible-blocks. Specifies the maximum number of reversible blocks beyond current LIB to allow before the node is gracefully shutdown.
Note:end