Incorporate Orleans.Redis providers

[EPinci]

Integrating Redis providers from Contrib repo as per #8207.

• Created Redis solution folder under Extensions
• Moved Directory provider under it
• Added Clustering, Persistence and Reminders providers
• Bumped StackExchange.Redis dependency to latest version
• Rewrote test integrating with Tester.Redis

Microsoft Reviewers: Open in CodeFlow

[EPinci]

@ReubenBond, @benjaminpetit, I rewrote all the Persistence, Reminders and Clustering test trying to derive from the bases in TesterInternal but I'm not sure I got them right - two have fixes outside the Redis code that need validation, one is still failing.

About the MultipleGrainDirectoryTests:
I found a typo here that should explain why the tests never run for Redis, I made a fix but I take that the same problem applies to the only other Directory provider using it, the Azure one.
On a hunch I would say that now this test could be failing for Azure as well. For some reasons the CI pipeline running on my PR skips the Azure tests so I cannot validate.
The test fails on this call but I have no clue on why.

About the Clustering/CleanupDefunctSiloEntries:
I made a fix in the Redis provider for it but... what is the right way it should behave?

• The base TesterInteranal class creates a stale dead silo, a stale joining silo and an active silo; expects the cleanup to end up with a single silo (removing both the stales).
• The former Redis code removed only stale dead silos (the joining one would remain there)
• The Azure code removes stale !dead silos
• The consul code removes silos with outdated IAmAliveTime timestamps, regardless of the state
• The IGrainDirectory interface comments says dead (only) but then the test assumes joining silos to be removed as well

About the Clustering/GetGateways:
I made a fix in the TesterInternal/MembershipTests/MembershipTableTestBase.cs but...

• The IGrainDirectory interface comments of InsertRow is ambiguous to me: point 3 does not clarify if the method or the caller is supposed to update the version - key is update as in "provide the version.Next()" versus update as in "persist the changed one"
• In the same MembershipTableTestBase above, L115 repeatedly calls InsertRow with the same version (the first call with an <0,0> version that breaks the Redis test) while, on L154 the same call is made with an "updated" version. Seems inconsistent to me and that is why I made the change above. Curiously, that fixes the Redis test while not breaking other providers tests (per above, cannot test Azure)
• The code implementation of InsertRow is very differently implemented across providers. More importantly, does seems to me that most of the provider actually implement version consistency check like Redis has - note that I'm not implying that the Redis code I'm merging has to be the correct one...

[benjaminpetit]

About the MultipleGrainDirectoryTests:

Yes, I can confirm that AzureMultipleGrainDirectoriesTests is failing too...

About the Clustering/CleanupDefunctSiloEntries:

I think it should remove dead and joining silos. Active entries should be voted dead first.

About the Clustering/GetGateways:

I don't think the IMembershipTable (not the IGrainDirectory, I assume it's an error?) should care about the value of TableVersion.Version. Only the etag should be used as a concurrency check. Asking @ReubenBond to confirm

[ReubenBond]

Only the etag should be used as a concurrency check. Asking @ReubenBond to confirm

Correct, as far as concurrency checks are concerned. If the value read has a version less than the previously read version, though, it will be ignored by the cluster since versions must be monotonically increasing.

[ReubenBond]

Functional are failing because some tests (Azure, Redis) are not being skipped when they don't have a connection string specified

[ReubenBond]

Fantastic work, @EPinci!