Calendar buttons submit the form

### Issue type

**I'm submitting a ...** (check one with "x")

* [x] bug report
* [ ] feature request

### Issue description

**Current behavior:**

If calendar component is used inside form, calendar buttons trigger submit event.

**Expected behavior:**

Calendar buttons should not emit any propagating events.

**Steps to reproduce:**

1. Use calendar in a form
2. Press any button (e.g., navigation buttons)
3. Page is reloaded since form is being submitted

**Related code:**
Each button should have an explicit type
```
...
```

### Other information:

**npm, node, OS, Browser**
```
Node, npm: `v16.14.0` and `8.3.1`
OS: macOS Monterey 12.3.1
Browser: Firefox 100
```

**Angular, Nebular**
```
Angular: 13.3.0
Nebular: 9.0.2
```