Mark @FlaggedApi flags as exported

An aconfig flag that is used together with @FlaggedApi must be marked as
`is_exported: true` to guarantee that the auto-generated lookup code
checks the actual flag value (instead of using a hard-coded value set at
compile time). This is important when the API is called across aconfig
container boundaries (e.g. a mainline module calling code on the system
partition).

Mark all non-exported flags used with @FlaggedApi as exported.

The "all @FlaggedApi flags are exported" invariant should be checked at
build time; this will be added in future CLs.

Bug: 378061535
Test: treehugger
Flag: EXEMPT can't flag changes to flag declarations
Change-Id: If3a1662486a914f97b2e3b3342223d5d5e114575
diff --git a/flags/telecom_resolve_hidden_dependencies.aconfig b/flags/telecom_resolve_hidden_dependencies.aconfig
index a120b85..e5bb1fb 100644
--- a/flags/telecom_resolve_hidden_dependencies.aconfig
+++ b/flags/telecom_resolve_hidden_dependencies.aconfig
@@ -16,4 +16,5 @@
     description: "Fixed read only flag used for setting up BlockedNumbersManager to be retrieved via context"
     bug: "325049252"
     is_fixed_read_only: true
+    is_exported: true
 }