Feat: several features added

packages/datastructure/lru_cache.go

packages/datastructure/lru_cache_test.go

packages/events/event_test.go

packages/iac/area.go

packages/iac/errors.go

packages/iac/iac.go

packages/iac/olc_conversion.go

packages/ternary/ternary.go

packages/transaction/transaction.go

plugins/tangle/api.go

plugins/tangle/approvers.go

plugins/tangle/approvers_test.go

plugins/tangle/database.go

plugins/tangle/mempool.go

plugins/tangle/plugin.go

plugins/tangle/solidifier.go

plugins/tangle/transaction.go

plugins/tangle/transaction_metadata.go