Upgrade to Gradle 7.0 (#1712)

* Convert to gradle 7.

* More fixes, regenerated lockfiles.

* Update lockfiles for dependency update.

* Fix show_upgrade_diff for new lockfile format

* Add property for allowInsecureProtocol

Allow us to override the restriction against use of plain HTTP for
communication to dependency repositories.  We need this to be able to use a
local proxy for dependency gathering.

* Checking in missing gradle.lockfile

config/nom_build.py

@@ -84,6 +84,10 @@ PROPERTIES = [
     Property('pluginsUrl',
              'URL to use for the gradle plugins repository (defaults to maven '
              'central, see also mavenUrl'),
+    Property('allowInsecureProtocol',
+             'Allow connecting to plain HTTP repositories.  This is provided '
+             'to allow us to communicate to a local proxy when doing '
+             'dependency updates.'),
     Property('uploaderDestination',
              'Location to upload test reports to.  Normally this should be a '
              'GCS url (see also uploaderCredentialsFile)'),