feat: split integrations.bitbucket -> bitbucketCloud / bitbucketServer

Split `integrations.bitbucket` into `integrations.bitbucketCloud`
and `integrations.bitbucketServer`
while staying backwards compatible for now
(== `BitbucketIntegration` loads from the new configs, too, if the old is not used).

Relates-to: #9923
Signed-off-by: Patrick Jungermann <Patrick.Jungermann@gmail.com>

.changeset/moody-suns-smell.md

@@ -0,0 +1,37 @@
+---
+'@backstage/integration': minor
+'@backstage/integration-react': minor
+---
+
+Split `bitbucket` integration into `bitbucketCloud` and `bitbucketServer`
+(backwards compatible).
+
+In order to migrate to the new integration configs,
+move your configs from `integrations.bitbucket`
+to `integrations.bitbucketCloud` or `integrations.bitbucketServer`.
+
+Migration example:
+
+**Before:**
+
+```yaml
+integrations:
+  bitbucket:
+    - host: bitbucket.org
+      username: bitbucket_user
+      appPassword: app-password
+    - host: bitbucket-server.company.com
+      token: my-token
+```
+
+**After:**
+
+```yaml
+integrations:
+  bitbucketCloud:
+    - username: bitbucket_user
+      appPassword: app-password
+  bitbucketServer:
+    - host: bitbucket-server.company.com
+      token: my-token
+```