Merge bitcoin/bitcoin#29535: ci: Fix functional tests step for pull requests in Windows GHA job

57e6e22 ci: Fix functional tests step for pull requests in Windows GHA job (Hennadii Stepanov)

Pull request description:

  This functionality has been broken since the Windows runner image version `20240128.1.0`.

  Fixes bitcoin/bitcoin#29534.

ACKs for top commit:
  fanquake:
    I can ACK 57e6e22 this only based on the fact that in this PR, the native Windows functional tests run: https://github.com/bitcoin/bitcoin/actions/runs/8119259315/job/22194887783#step:27:72, and that the native Windows functional tests are not currently running on master: https://github.com/bitcoin/bitcoin/actions/runs/8131828989/job/22239779585#step:27:63.
  hebasto:
    > I can ACK 57e6e22
  m3dwards:
    ACK bitcoin/bitcoin@57e6e22 as a way to get the tests running again quickly.

Tree-SHA512: 03e04fb96292e31ca0a8057e91b57f0812df92589f52f0602844e151ec5ec296badf5e549b1b606bab85607a3f9cd6abdfd328df80bf268501b537a596db0d96

Author: fanquake

.github/workflows/ci.yml

@@ -289,4 +289,5 @@ jobs:
       - name: Run functional tests
         env:
           TEST_RUNNER_EXTRA: ${{ github.event_name != 'pull_request' && '--extended' || '' }}
-        run: py -3 test\functional\test_runner.py --jobs $env:NUMBER_OF_PROCESSORS --ci --quiet --tmpdirprefix=$env:RUNNER_TEMP --combinedlogslen=99999999 --timeout-factor=$env:TEST_RUNNER_TIMEOUT_FACTOR $env:TEST_RUNNER_EXTRA
+        shell: cmd
+        run: py -3 test\functional\test_runner.py --jobs %NUMBER_OF_PROCESSORS% --ci --quiet --tmpdirprefix=%RUNNER_TEMP% --combinedlogslen=99999999 --timeout-factor=%TEST_RUNNER_TIMEOUT_FACTOR% %TEST_RUNNER_EXTRA%