Rename the bitbucket and github listers to remove the 'tld' part

so that we can easily manage its configuration (especially in the docker
environment) by referring to this lister as only 'bitbucket' everywhere
(ie. python package name and config file names).

swh/lister/bitbucket/lister.py

@@ -11,7 +11,7 @@ from swh.lister.core.indexing_lister import SWHIndexingHttpLister
 class BitBucketLister(SWHIndexingHttpLister):
     PATH_TEMPLATE = '/repositories?after=%s'
     MODEL = BitBucketModel
-    LISTER_NAME = 'bitbucket.com'
+    LISTER_NAME = 'bitbucket'
 
     def get_model_from_repo(self, repo):
         return {

swh/lister/github/lister.py

@@ -13,7 +13,7 @@ class GitHubLister(SWHIndexingHttpLister):
     PATH_TEMPLATE = '/repositories?since=%d'
     MODEL = GitHubModel
     API_URL_INDEX_RE = re.compile(r'^.*/repositories\?since=(\d+)')
-    LISTER_NAME = 'github.com'
+    LISTER_NAME = 'github'
 
     def get_model_from_repo(self, repo):
         return {