[lldb-dap] Fix TestDap_attach.py flakiness (#137278)

# Summary
This patch makes the `request_attach` wait for events `process` and
`initialized` just like `request_launch`. This ensure the DAP session
can move forward somewhat correctly.

Recently `TestDap_attach.test_terminate_commands` became flaky.
It's hitting:
```
lldbsuite/test/tools/lldb-dap/dap_server.py", line 350, in send_recv
    raise ValueError(desc)
ValueError: no response for "disconnect"
```
I took a look at the DAP msg from that test case and noticed:
- It's not using the regular attaching, instead it's using the
`attachCommands` to launch debug the binary and it will stop at entry.
- The `initialized` event returned after the `disconnect` request. Which
means lldb-dap didn't really get ready yet.

### NOTE
The `dap_server.py` is doing things to mimic the VSCode (or other dap
clients) but it had some assumptions. For example, it's still missing
the `configurationDone` request and response because it relies on a
continue action to trigger the `configurationDone` request.

# Test Plan
```
./bin/llvm-lit -va /Users/wanyi/llvm-upstream/llvm-project/lldb/test/API/tools/lldb-dap/attach/TestDAP_attach.py
./bin/llvm-lit -va /Users/wanyi/llvm-upstream/llvm-project/lldb/test/API/tools/lldb-dap/launch/TestDAP_launch.py
```

To test the `wait_for_events` timeout case
```
events = self.wait_for_events(["process", "initialized", "fake", "event"], 1)
if events:
    raise ValueError(f'no events {",".join(events)} found for within timeout 1')
```
Observed
<img width="696" alt="image"
src="https://github.com/user-attachments/assets/bc97c0ef-d91f-4561-8272-4d36f5f5d4e6"
/>

### Also
Looks like some test cases should be re-enabled in
0b8dfb5762
But only comments was removed. The skip statements survived the change.

lldb/packages/Python/lldbsuite/test/tools/lldb-dap/dap_server.py

@@ -380,6 +380,17 @@ class DebugCommunication(object):
             )
         return None
 
+    def wait_for_events(self, events, timeout=None):
+        """Wait for a list of events in `events` in any order.
+        Return the events not hit before the timeout expired"""
+        events = events[:]  # Make a copy to avoid modifying the input
+        while events:
+            event_dict = self.wait_for_event(filter=events, timeout=timeout)
+            if event_dict is None:
+                break
+            events.remove(event_dict["event"])
+        return events
+
     def wait_for_stopped(self, timeout=None):
         stopped_events = []
         stopped_event = self.wait_for_event(
@@ -618,7 +629,11 @@ class DebugCommunication(object):
         if gdbRemoteHostname is not None:
             args_dict["gdb-remote-hostname"] = gdbRemoteHostname
         command_dict = {"command": "attach", "type": "request", "arguments": args_dict}
-        return self.send_recv(command_dict)
+        response = self.send_recv(command_dict)
+
+        if response["success"]:
+            self.wait_for_events(["process", "initialized"])
+        return response
 
     def request_breakpointLocations(
         self, file_path, line, end_line=None, column=None, end_column=None
@@ -872,9 +887,7 @@ class DebugCommunication(object):
         response = self.send_recv(command_dict)
 
         if response["success"]:
-            # Wait for a 'process' and 'initialized' event in any order
-            self.wait_for_event(filter=["process", "initialized"])
-            self.wait_for_event(filter=["process", "initialized"])
+            self.wait_for_events(["process", "initialized"])
         return response
 
     def request_next(self, threadId, granularity="statement"):

lldb/test/API/tools/lldb-dap/attach/TestDAP_attach.py

@@ -93,7 +93,6 @@ class TestDAP_attach(lldbdap_testcase.DAPTestCaseBase):
         self.set_and_hit_breakpoint(continueToExit=True)
 
     @skipUnlessDarwin
-    @skipIfDarwin
     @skipIfNetBSD  # Hangs on NetBSD as well
     def test_by_name_waitFor(self):
         """
@@ -114,7 +113,6 @@ class TestDAP_attach(lldbdap_testcase.DAPTestCaseBase):
         self.attach(program=program, waitFor=True)
         self.set_and_hit_breakpoint(continueToExit=True)
 
-    @skipIfDarwin
     @skipIfNetBSD  # Hangs on NetBSD as well
     def test_commands(self):
         """
@@ -201,7 +199,6 @@ class TestDAP_attach(lldbdap_testcase.DAPTestCaseBase):
         self.verify_commands("exitCommands", output, exitCommands)
         self.verify_commands("terminateCommands", output, terminateCommands)
 
-    @skipIfDarwin
     @skipIfNetBSD  # Hangs on NetBSD as well
     @skipIf(
         archs=["arm", "aarch64"]