Fix flaky ServicePropertyDiscoveryConventionTest.Finds_service_properties_in_hierarchy

[Copilot]

Service_provider_cache_can_be_cleared calls Clear() on the global ServiceProviderCache.Instance singleton. When running concurrently with Finds_service_properties_in_hierarchy, the cache gets cleared between the two using blocks, causing the second context to resolve a new service provider with an empty in-memory store → 0 entries loaded.

• Root cause fix: Service_provider_cache_can_be_cleared now uses a local new ServiceProviderCache() — it's testing Clear() behavior, not the global singleton
• Defensive fix: ServicePropertiesContext now uses a shared InMemoryDatabaseRoot so the store survives service provider recreation

// Before: global singleton cleared during parallel test execution
var cache = ServiceProviderCache.Instance;
cache.Clear(); // races with any test relying on cached service providers

// After: isolated instance
var cache = new ServiceProviderCache();
cache.Clear();

[Copilot]

Pull request overview

Fixes a flaky test caused by concurrent clearing of the global ServiceProviderCache.Instance, which could force recreation of a service provider and unintentionally lose the InMemory store between two DbContext instances in the same test.

Changes:

• Updated Service_provider_cache_can_be_cleared to use an isolated new ServiceProviderCache() instance rather than the global singleton.
• Made ServicePropertiesContext use a shared InMemoryDatabaseRoot so the InMemory store survives service provider recreation during the test.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
test/EFCore.Tests/ServiceProviderCacheTest.cs	Avoids clearing the global cache by using a local ServiceProviderCache instance in the Clear() behavior test.
test/EFCore.Tests/Metadata/Conventions/ServicePropertyDiscoveryConventionTest.cs	Uses a shared InMemoryDatabaseRoot to keep InMemory data stable across multiple contexts even if the internal service provider changes.