Add a defs.bzl for pre-MODULE usage (#14)

Add a `defs.bzl` so that WORKSPACE users can `http_archive(name =
"aspect_tools_telemetry_report", ...)` in telemetry to satisfy load
statements while adopting telemetry in bzlmod.

### Changes are visible to end-users: no

### Test plan

TBD.

Author: arrdem

defs.bzl

@@ -0,0 +1,10 @@
+# A defs.bzl file allowing for WORKSPACE usage
+#
+# We don't (can't) collect telemetry in WORKSPACE systems. But we do want to be
+# able to deploy telemetry into rulesets which still provide WORKSPACE support
+# without injecting unsatisfied load() statements. This `defs.bzl` provides an
+# alternative to the one normally generated by the bzlmod extension so that
+# WORKSPACE users can `http_archive` in tools_telemetry and get a `defs.bzl`
+# approrpiate to satisfying any load() statements.
+
+TELEMETRY = 0