oeqa/selftest/wic: add test for excluding symlinks

oeqa/selftest/wic: add test for excluding symlinks

Add test to check if --exclude-path option can exclude symlinks. This
test validates commit[1].

Test result:
$ oe-selftest -r wic.Wic.test_exclude_path
2025-04-03 15:11:25,211 - oe-selftest - INFO - meta-selftest layer not found in BBLAYERS, adding it
2025-04-03 15:11:30,016 - oe-selftest - INFO - Adding layer libraries:
2025-04-03 15:11:30,017 - oe-selftest - INFO -  /buildarea/poky/meta/lib
2025-04-03 15:11:30,017 - oe-selftest - INFO - /buildarea/poky/meta-yocto-bsp/lib
2025-04-03 15:11:30,017 - oe-selftest - INFO - /buildarea/poky/meta-selftest/lib
2025-04-03 15:11:30,019 - oe-selftest - INFO - Checking base configuration is valid/parsable
NOTE: Starting bitbake server...
2025-04-03 15:11:31,652 - oe-selftest - INFO - Adding: "include selftest.inc" in /buildarea/poky/build-st/conf/local.conf
2025-04-03 15:11:31,653 - oe-selftest - INFO - Adding: "include bblayers.inc" in bblayers.conf
2025-04-03 15:11:31,653 - oe-selftest - INFO - test_exclude_path (wic.Wic)
2025-04-03 15:43:11,341 - oe-selftest - INFO -  ... ok
2025-04-03 15:43:11,341 - oe-selftest - INFO - ----------------------------------------------------------------------
2025-04-03 15:43:11,342 - oe-selftest - INFO - Ran 1 test in 1899.900s
2025-04-03 15:43:11,342 - oe-selftest - INFO - OK
2025-04-03 15:43:14,834 - oe-selftest - INFO - RESULTS:
2025-04-03 15:43:14,835 - oe-selftest - INFO - RESULTS - wic.Wic.test_exclude_path: PASSED (1899.69s)
2025-04-03 15:43:14,836 - oe-selftest - INFO - SUMMARY:
2025-04-03 15:43:14,836 - oe-selftest - INFO - oe-selftest () - Ran 1 test in 1899.900s
2025-04-03 15:43:14,836 - oe-selftest - INFO - oe-selftest - OK - All required tests passed (successes=1, skipped=0, failures=0, errors=0)

[1] https://git.openembedded.org/openembedded-core/commit/?id=42e829ac1e9d74646b6dfb327b18b15f6b0df60b

Signed-off-by: Yi Zhao <yi.zhao@windriver.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>