[feature] Revisit precedence of values assigned to requirements' options (ATM, hardcoded value in configure method cannot be overridden)

Right now a recipe can do:

def configure(self):
    self.options["mydep"].myoption = "value"

This has absolute precedence. It can never be overridden, even from command line doing -o mydep:myoption=othervalue

I would suggest to change this in Conan 2.0:

• This has the same precedence as defining it in default_options, can be overriden by command line
• Recipes will be able to validate(), post graph expansion and raise if they do not accept some upstream configuration.

[jgsogo]

Unfortunately, Conan v1.x is not enforcing the scope for some attributes (access and modification) and it hasn’t been exhaustively documented, so we feel like changing it (or being more strict) might be considered breaking. Conan v2 should enforce it and make available to each function only the attributes that can be modified. At some point in time we will be more strict in ConanCenter so we detect these errors and fix them before moving to Conan 2.0 (probably we will take advantage of CONAN_V2_MODE variable).

[SpaceIm]

I misunderstood, sorry, so this modification sounds good to me 😃