Add prng_seeder to base PRODUCT_PACKAGES.

Cherry-pick / Dr No note: Should have been included with
the previous prng_seeder CLs but we missed that it was needed
due to testing on branches without prebuilts.

Needs to be on all (for now) devices with libcrypto, i.e. all
of them.

I failed to learn from https://r.android.com/1305853 that
adding something to Conscrypt's requirements doesn't work if
the module is coming from a prebuilt...

Again, the correct solution here would actually be to make
libcrypto rather than Conscrypt require prng_seeder but Soong
considers that a circular dependency

Bug: 243933553
Test: m installclean && m and verify prng_seeder is installed and running.
Change-Id: Ie34f8c693469eaeedae6a010b956d6c6513a6b15
Merged-In: Ie34f8c693469eaeedae6a010b956d6c6513a6b15
(cherry picked from commit 19b3361a020860edc9b3a39e36e229520675466c)
diff --git a/target/product/base_system.mk b/target/product/base_system.mk
index de32171..b0870c3 100644
--- a/target/product/base_system.mk
+++ b/target/product/base_system.mk
@@ -238,6 +238,7 @@
     pppd \
     preinstalled-packages-platform.xml \
     privapp-permissions-platform.xml \
+    prng_seeder \
     racoon \
     recovery-persist \
     resize2fs \