Emit Event on Shared Signer Configuration

[nlordell]

Fixes hats-finance#3

This PR adds an event that is emitted on shared signer configuration. Note that the event is emitted in the context of the configured Safe account. In order to prevent event topic0 collisions, we chose an explicitly verbose name.

With respect to indexing, we explicitly chose not to index any of the fields so that it matches the Created event:

safe-modules/modules/passkey/contracts/interfaces/ISafeSignerFactory.sol

Lines 13 to 20 in bb5e1f7

	/**
	* @notice Emitted when a new signer is created.
	* @param signer The signer address.
	* @param x The x-coordinate of the public key.
	* @param y The y-coordinate of the public key.
	* @param verifiers The P-256 verifiers to use.
	*/
	event Created(address indexed signer, uint256 x, uint256 y, P256.Verifiers verifiers);

To re-iterate on the reasons we chose to not index some of the fields (same reasoning applies to Created event above):

• x and y: These are single-use public key coordinates attached to a passkey. It doesn't make sense to filter events by "all events with x value", or similarly "all events with y value". Furthermore, you can compute the signer (which is indexed in the Created event) from the key coordinates, so you can to some degree search for signers for a given key coordinate.
• verifiers: This felt more like a configuration than something that Dapps would need to filter by. Why it might be interesting to see on chain which verifiers are being used, tools like Dune can help with this, and the additional cost of an indexed field is not worth it in our opinion.