This change introduces templates for HashtableCapacity, PerTableSeed, and HashtableInlineData to allow for storing capacity as either a full size_t or as a log2 value in a single byte.
`kCapacityAsOneByte` is not possible to propagate to raw_hash_set. The classes are only used in tests.
In kCapacityAsOneByte mode, seed is reduced to 8 bits.
NextHashTableSeed always return 16 bit for simplicity.
PiperOrigin-RevId: 907151369
Change-Id: Iec812b3d564adb3c96d99f11754e116f38848829
a4ca419989