Libmodulemd: libmodulemd: out-of-bounds read when emitting rpm-map artifacts

A flaw was found in libmodulemd. In the module stream v2 rpm-map emission path, an inner loop incorrectly uses the count of digest algorithms as its bound instead of the number of checksums in the current digest table. Crafted modulemd v2 metadata with multiple digest types can trigger an out-of-bounds read during YAML serialization, typically causing a crash and resulting in a denial of service.