SQLite backed cache

[moio]

Issue: rancher/rancher#45635
Refers to the Informer-based, SQLite-backed Steve caching ("Vai") RFC

Reviewer notes:

• A lot of this PR is tests - starting with non-testing files at first should simplify review.

• the main entry point to Steve, ToServer, has been duplicated with a ToServerAlpha func, and with it all subsequent code, so that the existing cache codebase and the SQLite backed cache codebase can coexist in parallel and be activated by feature flags. Therefore:

  • pkg/server/cli/clicontext.go, pkg/server/server.go, pkg/resources/schema.go, pkg/resources/common/formatter.go contain patched copies of the original methods adapted for the new SQLite-backed cache exposed by lasso. The one with non-trivial changes is server.go's setupAlpha
  • all other changes are self contained in the stores/partitionalpha and stores/proxyalpha directories, both intended to be drop in replacements of the original stores/partition and stores/proxy
  • something like kdiff3 ./pkg/stores/proxy ./pkg/stores/proxyalpha and kdiff3 ./pkg/stores/partition ./pkg/stores/partitionalpha can help making sense of differences
    • eg. pkg/stores/proxyalpha/error_wrapper.go, pkg/stores/proxyalpha/watch_refresh.go and pkg/stores/proxyalpha/unformatter.go are exact copies of the originals (plus convenience constructors). Therefore the only relevant file difference is in proxy_store.go

[rmweir]

@MbolotSuse we spoke about this but so its documented here, I think changing how the code is separated (alpha and non-alpha atm) would be fine. Similarly, I think not using the term alpha is fine. This approach was to prevent regression by not commiting any change tot he active, production code-path. A diff could be viewed by PRing a fork where the alpha packages replace their corresponding non-alpha counterparts. Either way I think anything is fine, however you @moio and @moio choose to handle it.

[tomleb]

One question about the metadata fields. Still reviewing the rest. And one suggestion that's not very important.

[moio]

Alpha is not a descriptive name, we should improve that

All prefixes changed to "sql" as suggested.

There's a lot of duplicated code, we should aim to remove that.

Several of the last commits take care of most duplication, especially in code not expected to change. Feel free to point out other cases going forward.

[moio]

Resolved many points, all of those still unresolved have been moved to the follow-up epic issue. Merging.