Prior to this change, all alert instance writes and deletes happened
individually, in their own database transaction. This change batches up
writes or deletes for a given rule's evaluation loop into a single
transaction before applying it.
These new transactions are off by default, guarded by the feature toggle "alertingBigTransactions"
Before:
```
goos: darwin
goarch: arm64
pkg: github.com/grafana/grafana/pkg/services/ngalert/store
BenchmarkAlertInstanceOperations-8 398 2991381 ns/op 1133537 B/op 27703 allocs/op
--- BENCH: BenchmarkAlertInstanceOperations-8
util.go:127: alert definition: {orgID: 1, UID: FovKXiRVzm} with title: "an alert definition FTvFXmRVkz" interval: 60 created
util.go:127: alert definition: {orgID: 1, UID: foDFXmRVkm} with title: "an alert definition fovFXmRVkz" interval: 60 created
util.go:127: alert definition: {orgID: 1, UID: VQvFuigVkm} with title: "an alert definition VwDKXmR4kz" interval: 60 created
PASS
ok github.com/grafana/grafana/pkg/services/ngalert/store 1.619s
```
After:
```
goos: darwin
goarch: arm64
pkg: github.com/grafana/grafana/pkg/services/ngalert/store
BenchmarkAlertInstanceOperations-8 1440 816484 ns/op 352297 B/op 6529 allocs/op
--- BENCH: BenchmarkAlertInstanceOperations-8
util.go:127: alert definition: {orgID: 1, UID: 302r_igVzm} with title: "an alert definition q0h9lmR4zz" interval: 60 created
util.go:127: alert definition: {orgID: 1, UID: 71hrlmR4km} with title: "an alert definition nJ29_mR4zz" interval: 60 created
util.go:127: alert definition: {orgID: 1, UID: Cahr_mR4zm} with title: "an alert definition ja2rlmg4zz" interval: 60 created
PASS
ok github.com/grafana/grafana/pkg/services/ngalert/store 1.383s
```
So we cut time by about 75% and memory allocations by about 60% when
storing and deleting 100 instances.
* Move annotation functionality behind a history persistence interface
* Rename to RecordState
* Fix lint error in import aliasing
* One more import linter error
* Refactor state manager to not depend on rule store interface
* Refactor grafana and proxied ruler APIs to not depend on store.RuleStore
* Refactor folder subscription logic to not use store.RuleStore
* Delete dead code
* Delete store.RuleStore
* Add consumer-side store interface to state manager
* Remove dead dependency
* Delete dead dependency in API struct
* Delete store-layer InstanceStore interface
* Move fake for state's InstanceStore interface to state package
