Support msg.sender fuzzing about medusa

[Xenomega]

Not exactly, we wouldn't want to add that anything to the config except a boolean (and maybe probability) for this at most, the "hardcoded/magic addresses" part of my post referred to using address literals in the codebase as msg.sender. I imagine for now it would have to be echidna-slither-printer-provided addresses extracted at runtime so we don't use too many unrelated values as addresses (currently our built-in AST literal extraction just takes every int and converts it to an address to handle address(0x123) for instance). But this would require a larger change with funding at genesis in this mode, so I'm also not sure we'd want to tackle it now. Anish has a PR for the echidna slither printer we should probably merge in before this.

Note: we'll probably want to make whatever change we have for funding at runtime here flexible enough that later we can use the same code paths to fund addresses used as deployers in "complex contract deployments" (etheno layer) we'll add after cheat codes and another PR or two.

Basically:

• Fuzzer compiles targets
• Address literals in BaseValueSet are added to Fuzzer.Senders prior to funding
• They are all then used

Or if you wanted to make it weighted differently (not sure if we'd want this), you'd fund all addresses in the BaseValueSet and periodically pull from there directly (not changing Fuzzer.Senders)

[ahpaleus]

I implemented it to use hardcoded/magic addresses from the configuration file with appropriate probability:

		"magicAddresses": {
			"enabled": true,
			"hardcodedAddresses": [
				"0x0000000000000000000000000000000000000000",
				"0xffffffffffffffffffffffffffffffffffffffff"
			],
			"probability": 0.5
		},

and based on this probobability, the selectedSender is chosen in the generateFuzzedCall between one of the "senderAddreses" or "hardcodedAddresses".

@Xenomega - Is this the assumption that you had in mind? Also, should I implement fuzzing the msg.sender address itself if it comes from the "hardcodedAddresses" pool??