fix: update drawings for specs and add context for sub module interfaces

standard/ERCs/erc-6900.md

@@ -74,14 +74,7 @@ A call to the smart contract account can be broken down into the steps as shown
 
 ![diagram showing call flow within an modular account](../assets/eip-6900/Modular_Account_Call_Flow.svg)
 
-The following diagram shows permitted module execution flows. During a module's execution step from the above diagram, the module may perform a "Module Execution Function", using either `executeFromModule` or `executeFromModuleExternal`. These can be used by modules to execute using the account's context.
-
-- `executeFromModule` handles calls to other installed module's execution function on the modular account.
-- `executeFromModuleExternal` handles calls to external addresses.
-
-![diagram showing a module execution flow](../assets/eip-6900/Module_Execution_Flow.svg)
-
-Each step is modular, supporting different implementations for each execution function, and composable, supporting multiple steps through hooks. Combined, these allow for open-ended programmable accounts.
+Each step is modular, supporting different implementations, that allows for open-ended programmable accounts.
 
 ### Interfaces
 
@@ -322,6 +315,8 @@ interface IModule is IERC165 {
 
 #### `IValidationModule.sol`
 
+Validation module interface. Modules **MAY** implement this interface to provide validation functions for account.
+
 ```solidity
 interface IValidationModule is IModule {
     /// @notice Run the user operation validation function specified by the `entityId`.
@@ -373,6 +368,8 @@ interface IValidationModule is IModule {
 
 #### `IValidationHookModule.sol`
 
+Validation hook module interface. Modules **MAY** implement this interface to provide hooks for validation functions for account.
+
 ```solidity
 interface IValidationHookModule is IModule {
     /// @notice Run the pre user operation validation hook specified by the `entityId`.
@@ -420,6 +417,8 @@ interface IValidationHookModule is IModule {
 
 #### `IExecutionModule.sol`
 
+Execution module interface. Modules **MAY** implement this interface to provide execution functions for account.
+
 ```solidity
 struct ManifestExecutionFunction {
     // The selector to install
@@ -456,6 +455,8 @@ interface IExecutionModule is IModule {
 
 #### `IExecutionHookModule.sol`
 
+Execution hook module interface. Modules **MAY** implement this interface to provide hooks for execution functions for account.
+
 ```solidity
 interface IExecutionHookModule is IModule {
     /// @notice Run the pre execution hook specified by the `entityId`.