app/testpmd: add record-burst-stats runtime config

app/testpmd: add record-burst-stats runtime config

Convert CONFIG_RTE_TEST_PMD_RECORD_BURST_STATS to a
runtime configuration.

Signed-off-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
Tested-by: Phil Yang <phil.yang@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>