cache visitor ID on first use

```diff
import ytmusicapi
import timeit

yt = ytmusicapi.YTMusic()
for _ in range(2):
  round(timeit.timeit(lambda: yt.get_album('MPREb_4pL8gzRtw1p'), number=1) * 1000)

-710
-593
+753
+146
```

ytmusicapi/ytmusic.py

@@ -150,6 +150,8 @@ def __init__(
             except KeyError:
                 raise YTMusicUserError("Your cookie is missing the required value __Secure-3PAPISID")
 
+        self.visitor_id = None
+
     @property
     def base_headers(self) -> CaseInsensitiveDict:
         if self.auth_type == AuthType.BROWSER or self.auth_type == AuthType.OAUTH_CUSTOM_FULL:
@@ -168,10 +170,11 @@ def base_headers(self) -> CaseInsensitiveDict:
 
     @property
     def headers(self) -> CaseInsensitiveDict:
-        headers = self.base_headers
+        visitor_id = self.visitor_id or get_visitor_id(partial(self._send_get_request, use_base_headers=True))
+        self.visitor_id = visitor_id
 
-        if "X-Goog-Visitor-Id" not in headers:
-            headers.update(get_visitor_id(partial(self._send_get_request, use_base_headers=True)))
+        headers = self.base_headers
+        headers.update(visitor_id)
 
         # keys updated each use, custom oauth implementations left untouched
         if self.auth_type == AuthType.BROWSER: