Announce the library name without demanding IDatabase

[mgravell]

(specifically: support WithRetry)

Note: takes SE.Redis 3.1.3

Auxiliary.ExecuteAsync unconditionally cast its IDatabaseAsync to IDatabase in order to send the one-time CLIENT SETINFO lib-name/lib-ver pair. A retry-wrapped database (SE.Redis 3.1.0 WithRetry) is async-only - RetryDatabase implements IDatabaseAsync but not IDatabase - so every async module command issued through one threw InvalidCastException before the command was sent, making the retry categories added in #540 unusable from the async API.

The announcement never needed the sync interface: it only needed it to create a batch to group the two commands, which don't need grouping. It is now typed as IDatabaseAsync and dispatched fire-and-forget via an internal ClientSetInfoAsync overload that takes dispatch flags, so there is no cast, no batch, and no round-trip on the caller's first command. In the expected case - fire-and-forget completing synchronously - no state machine is entered on this path at all: the overload hands back a cached completed task, and the caller only awaits (to consume a fault) if a task somehow comes back not-yet-completed. A synchronous failure in the version probe can no longer fail the caller's command either; announcing who we are is best-effort.

Renamed SetInfoInPipeline -> SetLibraryInfoOnce (internal): there is no longer a pipeline involved.

Task.IsCompletedSuccessfully only exists on modern .NET, so netstandard2.0/net481 get it as an extension property polyfill rather than open-coding the Status test at each site.

Audited the rest of the library for the same shape: this was the only unconditional cast to a sync SE.Redis interface; SearchCommandsAsync's cluster cursor path was already type-tested.

Tests cover an async module command and the first-use announcement over db.WithRetry(...) - both fail with InvalidCastException before this change - plus the synchronous completion that the fire-and-forget dispatch relies on.

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Note

Medium Risk
Touches first-command behavior on every connection and transaction edge cases for library announcement; dependency bump to experimental WithRetry APIs affects all consumers.

Overview
Fixes async module commands on db.WithRetry(...) by removing the IDatabase cast in the one-time CLIENT SETINFO announcement. SetLibraryInfoOnce (renamed from SetInfoInPipeline) runs on IDatabaseAsync, sends lib-name/lib-ver as fire-and-forget (no batch, no extra round-trip on the caller’s first command), and skips ITransactionAsync so SETINFO is not queued into MULTI/EXEC; announcement failures are best-effort.

Adds an internal ClientSetInfoAsync(..., CommandFlags) fast path for synchronous fire-and-forget completion, a Task.IsCompletedSuccessfully polyfill for netstandard/net481, and WithRetryTests for retry DB/transactions and transaction announcement behavior.

Dependency: StackExchange.Redis 3.0.25 → 3.1.3; CommandCategories now aliases CommandFlags.CommandRetry* (drops int casts); SER007 suppressed repo-wide; test projects use central package version (no 3.1.0 override).

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