Add parameterless overloads for AddPooledDbContextFactory<TContext>

[bkarakaya01]

Summary

Introduces two new overloads (parameterless + poolSize) that delegate to the existing
(IServiceProvider, DbContextOptionsBuilder) overload with a no-op action.

Aligns pooled factory ergonomics with the centralized configuration model
ConfigureDbContext<TContext>.

Keeps full backward compatibility; no existing signature or behavior changed.

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Motivation

When using ConfigureDbContext<TContext>, callers shouldn’t have to pass an extra configuration lambda
to pooled factory registration; options should flow automatically.

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Design

• New overloads simply call the existing overload with static (_, __) => { }.
• XML docs reference the related ConfigureDbContext overload; no behavioral drift.
• No changes to pooling internals, service lifetimes, or registrations.

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Tests

Added AddPooledDbContextFactoryParameterlessTest covering:

• ✅ Parameterless factory honors ConfigureDbContext provider (InMemory).
• ✅ Custom poolSize overload resolves correctly.
• ✅ Scoped resolution of TContext works.
• ✅ Pool is registered as singleton.
• ✅ Without configuration, first provider use throws.

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Compatibility

• Additive public API only.
• No source or binary breaking changes.
• Full XML documentation provided for all new public members.

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Issues

Fixes #34658

[bkarakaya01]

@dotnet-policy-service agree