feat: send test mail (#7968)

# Which Problems Are Solved

- Zitadel doesn't have a way to test SMTP settings either before
creating a new provider or once the SMTP provider has been created.
- Zitadel SMTP messages can be more informative for usual errors

# How the Problems Are Solved

- A new step is added to the new/update SMTP provider wizard that allows
us to test a configuration. The result is shown in a text area.
- From the table of SMTP providers you can test your settings too.
- The email address to send the email is by default the email address
for the logged in user as suggested.
- Some of the SMTP error messages have been changed to give more
information about the possible situation. For example: could not contact
with the SMTP server, check the port, firewall issues... instead of
could not dial

Here's a video showing this new option in action:


https://github.com/zitadel/zitadel/assets/30386061/50128ba1-c9fa-4481-8eec-e79a3ca69bda

# Additional Changes

Replace this example text with a concise list of additional changes that
this PR introduces, that are not directly solving the initial problem
but are related.
For example:
- The docs explicitly describe that the property XY is mandatory
- Adds missing translations for validations.

# Additional Context

- Closes #4504

console/src/assets/i18n/nl.json

@@ -486,6 +486,7 @@
     "MORE": "meer",
     "STEP": "Stap",
     "SETUP": "Instellen",
+    "TEST": "Test",
     "UNSAVEDCHANGES": "Niet-opgeslagen wijzigingen",
     "UNSAVED": {
       "DIALOG": {
@@ -2256,6 +2257,7 @@
       "ACTIVATED": "Geactiveerd",
       "ACTIVATE": "Aanbieder activeren",
       "DEACTIVATE": "Aanbieder deactiveren",
+      "TEST": "Test uw aanbieder",
       "TYPE": "Type",
       "DIALOG": {
         "ACTIVATED": "SMTP-configuratie is geactiveerd",
@@ -2279,7 +2281,6 @@
         "CURRENT_DESC_TITLE": "Dit zijn uw SMTP-instellingen",
         "PROVIDER_SETTINGS": "SMTP-providerinstellingen",
         "SENDER_SETTINGS": "Afzenderinstellingen",
-        "TEST_SETTINGS": "SMTP-instellingen testen",
         "NEXT_STEPS": "Volgende stappen",
         "ACTIVATE": {
           "TITLE": "Activeer uw SMTP-provider",
@@ -2288,6 +2289,12 @@
         "DEACTIVATE": {
           "TITLE": "Deactiveer uw SMTP-provider",
           "DESCRIPTION": "Als u deze SMTP-provider deactiveert, kan ZITADEL deze niet gebruiken om meldingen te verzenden totdat u deze opnieuw activeert."
+        },
+        "SAVE_SETTINGS": "Sla uw instellingen op",
+        "TEST": {
+          "TITLE": "Test uw instellingen",
+          "DESCRIPTION": "U kunt de instellingen van uw SMTP-provider testen en het testresultaat controleren voordat u deze opslaat",
+          "RESULT": "Je email is succesvol verzonden"
         }
       }
     },