Add a validation phase for the resolved configuration

[fvictorio]

We validate the values provider in the user config, but not the ones that result after resolving the configuration (using our resolution and the config extenders). This is a blocker for #3323 and makes #3488 harder to do.

We should add something like validateResolvedConfig(resolved) after this:

hardhat/packages/hardhat-core/src/internal/core/config/config-loading.ts

Lines 107 to 109 in a1a36f8

	for (const extender of HardhatContext.getHardhatContext().configExtenders) {
	extender(resolved, frozenUserConfig);
	}

Validating the number of optimizer runs (#3488) is easy and low risk, so maybe that could be the first validation included there.