Terminate the ledger by default if the Tendermint version is not compatible

[james-chf]

After https://github.com/anoma/namada/pull/522, the ledger will check if the tendermint binary being used is officially compatible (i.e. the version string emitted by tendermint version matches what the ledger expects), and if not, log a warning. We should change the ledger to exit instead of logging a warning by default, to avoid tendermint/ directories getting accidentally clobbered and fail fast if the wrong version of tendermint is being used for some reason.

Very importantly, there needs to be an easy way to override this so custom builds can be used if desired (e.g. during development). We could add a new ledger config option e.g. ledger.tendermint.check_version which is true by default. This could then be overridden easily by using an envvar like ANOMA_LEDGER__TENDERMINT__CHECK_VERSION=false.