Add splitTestsCompilation solidity setting (1): Configuration updates

[alcuadrado]

This PR introduces the new config, it's validation, and resolution

[changeset-bot]

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Latest commit: be8bf71

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[Copilot]

Pull request overview

Adds a new splitTestsCompilation Solidity setting to Hardhat’s Solidity plugin configuration surface, including user-config type extensions, config schema validation, and resolved-config shaping, with accompanying test updates.

Changes:

• Extend Solidity config typings to include splitTestsCompilation (user + resolved config).
• Validate splitTestsCompilation as an optional boolean across supported Solidity config shapes.
• Resolve splitTestsCompilation into the final solidity config with a default of false, and update tests/fixtures accordingly.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
packages/hardhat/test/internal/builtin-plugins/solidity/config.ts	Adds validation + resolution test coverage for splitTestsCompilation, and updates resolved-config test fixture.
packages/hardhat/test/internal/builtin-plugins/solidity/build-system/build-system.ts	Updates SolidityConfig test fixture to include required splitTestsCompilation.
packages/hardhat/src/internal/builtin-plugins/solidity/type-extensions.ts	Extends CommonSolidityUserConfig and resolved SolidityConfig types with splitTestsCompilation.
packages/hardhat/src/internal/builtin-plugins/solidity/config.ts	Adds Zod schema validation for splitTestsCompilation and resolves it into SolidityConfig with default false.

[schaable]

LGTM