scripts: add execute_bisection.sh for git bisect-based regression detection

Adds a new helper script to support automated kernel regression
bisection using 'git bisect run'.

The script builds the kernel using build_local_kernel.sh, exports
kernel image and modules path, then runs benchmarks using
'fastpath bisect run'. It captures and propagates the exit status
from fastpath, enabling correct signaling to git bisect:

  0 => improvement or no change (good)
  1 => regression (bad)
  125 => skip (no data or filter mismatch)

This supports fast identification of performance regressions
across kernel versions.

Signed-off-by: Aishwarya TCV <aishwarya.tcv@arm.com>