release-config: use ${TARGET_RELEASE} for output

When the passed release name is an alias, write
release_config-PRODUCT-RELEASE.mk using the alias, since that is where
core/release_config.mk is going to look for it.

Bug: 328495189
Test: manual
Ignore-AOSP-First: cherry-pick
Merged-In: I4e6909f43bf136974323754e06fa538e39e0faab
Change-Id: I4e6909f43bf136974323754e06fa538e39e0faab