chore(release): bumped version to v1.5.11

fix(memory): panic on plain values with reflect.Elem()

reflect.Value.Elem() panics when called on non-pointer types (string,
int, bool, etc.). When a plain value is stored via Set() and retrieved
via Get(), the old code unconditionally called v.Elem() which crashes
with 'reflect: call of reflect.Value.Elem on string Value'.

Fix: check stored value kind before calling Elem(). Only dereference
if it's a pointer; set plain values directly.

Tests: added 12 memory-specific tests covering plain string/int/bool/
slice Get/Set, TTL expiry, Size/Keys/Clear/Overwrite. Added shared
RunPlainValuesTestCase to test suite covering 7 value types.

chore(release): bumped version to v1.5.9

chore(release): bumped version to v1.5.8

chore(release): bumped version to v1.5.7

chore(release): bumped version to v1.5.6

chore(release): bumped version to v1.5.5

chore(release): bumped version to v1.5.4

chore(release): bumped version to v1.5.3

chore(release): bumped version to v1.5.2