feat: rewrite statistics structures using generic logic

sbroad-cartridge/src/cartridge/router.rs

sbroad-core/src/cbo.rs

sbroad-core/src/cbo/helpers.rs

sbroad-core/src/cbo/helpers/tests.rs

sbroad-core/src/cbo/histogram.rs

sbroad-core/src/cbo/histogram/tests.rs

sbroad-core/src/cbo/tests.rs

sbroad-core/src/executor/engine.rs

sbroad-core/src/executor/engine/mock.rs

sbroad-core/src/ir/value.rs

sbroad-core/src/ir/value/tests.rs