Add feature flag for reducing randomness in memalloc test

[aditijannu]

No description provided.

[NirjharRoyiitk]

Minor: Can we have the size conditionally defined in the match case before this? Since both the size and the layout is being conditionally defined, I was thinking if we can have the size in the condition block this

/* Create a random size depending on the memory type */
        let (scan_interval, mut size, limit) = match memsize {
            MemSize::Large => {
                (
                    SCAN_INTERVAL_LARGE_THREAD,
                    #[cfg(feature = "reduce_randomness")] {crate::TO_GB * 1} 
                    #[cfg(not(feature = "reduce_randomness"))] {TO_GB * get_random_num(LARGE_THREAD_MEM_START, LARGE_THREAD_MEM_END)},
                    LIMIT_LARGE_THREAD,
                )
            }
            MemSize::Medium => {
                (
                    SCAN_INTERVAL_MEDIUM_THREAD,
                    // similarly for medium and small threads
                    TO_MB * get_random_num(MEDIUM_THREAD_MEM_START, MEDIUM_THREAD_MEM_END),
                    LIMIT_MEDIUM_THREAD,
                )
            }
            MemSize::Small => {
                (
                    SCAN_INTERVAL_SMALL_THREAD,
                    TO_KB * get_random_num(SMALL_THREAD_MEM_START, SMALL_THREAD_MEM_END),
                    LIMIT_SMALL_THREAD,
                )
            }
        };