modem/modem_log_constants: create common folder

A lot of different modem related processes require reading / writing to
the same android system properties. This CL solifies them all into
one place to avoid duplication.

Test: build
Bug: 302435001
Change-Id: I113f43bb68833224f45ad91668cd327587e1649b

modem/modem_log_constants/Android.bp

@@ -0,0 +1,9 @@
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+cc_library {
+    name: "modem_log_constants",
+    export_include_dirs: [ "include" ],
+    vendor_available: true,
+}