Preserve per-block Func vars during lazy scope cleanup (fix Benchmarks regression)

[NikolayPianikov]

Motivation

• A recent cleanup started removing the active lazy/local-scope variable unconditionally for non-persistent lifetimes, which regressed ShouldSupportFuncWhenPerBlock by causing repeated constructions of Service3 instead of reusing the per-block factory value.
• The intent is to keep the protection against leaking override-constructed temporary vars while preserving legitimate per-block Func<T> variables across lazy scope restoration.

Description

• Tighten cleanup in VarsMap.RemoveNewNonPersistentVars so the current scope variable (the one identified by var.Declaration.Node.BindingId) is not removed for normal non-persistent lifetimes, and is only removed when it was created via an override construct (MdConstructKind.Override).
• Maintain the existing snapshot behavior that excludes override-constructed nodes from state snapshots so override-created vars still do not leak across scopes; the change only relaxes removal for the active per-block factory var.
• File changed: src/Pure.DI.Core/Core/Code/VarsMap.cs (logic in CreateState / RemoveNewNonPersistentVars).

Testing

• Could not run dotnet test in this environment because the .NET SDK is unavailable, so no automated test execution was performed here (tooling error: dotnet: command not found).
• Performed static validations and local inspections: examined VarsMap.cs lines around CreateState and RemoveNewNonPersistentVars, confirmed the logic now preserves per-block factory vars while still targeting override-constructed vars for removal.
• Located the relevant failing tests (ShouldSupportFuncWhenPerBlock and ShouldSupportOverrideInFactoryWithLocalFunctionAndFuncArgs) and verified the change addresses the per-block reuse regression by reasoning over the generation/restoration code paths.

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Codex Task