Rework integration tests

[Pasu4]

Integration tests are currently very behind the state of the extension (using old action names and deprecated handler functions). Also they're kind of messy as all actions of a category are in the same file (which also doesn't respect the recent category split of read/write file actions). The rework would rearrange the tests like so:

suite
+-- actions
    +-- edit_files
    |   +-- insert_text.test.ts
    |   +-- insert_lines.test.ts
    |   +-- ...
    +-- read_files
    |   +-- ...
    +-- ...

That should make it easier to manage tests.
There also should be a better system for simulating an action or parts of its lifecycle, since currently it still relies on the deprecated handler functions from before the standard schema implementation.

Suggestion for helper functions

type ActionSimulationResult = {
    failurePoint: 'none';
} | {
    failurePoint: 'validator';
    validationResult: ActionValidationResult;
} | {
    failurePoint: 'handler';
    handlerResult: ActionHandlerResult;
} | {
    failurePoint: 'cancelEvent';
    cancelEvent: RCECancelEvent;
};

// Simulate an action as if Neuro executed it in Autopilot mode
async function simulateAction<TParams extends ActionData['params']>(
    action: RCEAction<unknown, SchemaTypes, TParams>,
    params: TParams,
    timeout: number,
): ActionSimulationResult;

// Validate the action using sync and async validators
async function simulateActionValidators<TParams extends ActionData['params']>(
    action: RCEAction<unknown, SchemaTypes, TParams>,
    params: TParams,
    timeout: number,
): ActionSimulationResult;

// Simulate an action as if Neuro executed it in Autopilot mode, skipping over validation
async function simulateActionExecution<TParams extends ActionData['params']>(
    action: RCEAction<unknown, SchemaTypes, TParams>,
    params: TParams,
    timeout: number,
): ActionSimulationResult;

// Only register cancellation events and wait
async function simulateActionCancellation<TParams extends ActionData['params']>(
    action: RCEAction<unknown, SchemaTypes, TParams>,
    params: TParams,
    timeout: number,
): ActionSimulationResult;

[KTrain5169]

In general I think the RCEActionHandler function should only be the production assembly of the RCE lifecycle components.
Each component of the lifecycle should be implemented as a separate function per lifecycle component (perhaps multiple functions per component), since this not only helps us test parts of an action's RCE lifecycle, but also allows us to unit test the actual components themselves, and also makes it easy to debug the extension in the development host by easily disabling parts of the lifecycle by simply commenting out the relevant function.