Use DEFAULT_POLICY_TEST_STAGE constant

What does this MR do and why?

This MR addresses #446292 (closed) by using the ::Gitlab::Ci::Config::SecurityOrchestrationPolicies::Processor::DEFAULT_POLICY_TEST_STAGE constant instead of a string.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #446292 (closed)

changed milestone to %17.2

added Category:Security Policy Management devopssecure groupsecurity policies maintenancerefactor sectionsec typemaintenance labels

assigned to @Andyschoenen

added pipelinetier-1 label

added backend label

Reviewer roulette

Category	Reviewer	Maintainer
backend	@tvellishetty (UTC+5.5, 3.5 hours ahead of author)	@rkumar555 (UTC+2, same timezone as author)

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Generated by Danger

Hi @shreyasagarwal can you do the initial review?

requested review from @shreyasagarwal

approved this merge request

added pipeline:mr-approved label

added pipelinetier-2 label and removed pipelinetier-1 label

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• You are the last maintainer of this merge request
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@drew Could you please take over as the maintainer for the MR?

requested review from @drew and removed review request for @shreyasagarwal

E2E Test Result Summary

allure-report-publisher generated test report!

e2e-test-on-gdk: test report for ee0a55ce

expand test summary

+------------------------------------------------------------------+
|                          suites summary                          |
+-------------+--------+--------+---------+-------+-------+--------+
|             | passed | failed | skipped | flaky | total | result |
+-------------+--------+--------+---------+-------+-------+--------+
| Govern      | 65     | 0      | 0       | 0     | 65    | ✅     |
| Plan        | 60     | 0      | 2       | 0     | 62    | ✅     |
| Create      | 126    | 0      | 11      | 0     | 137   | ✅     |
| Verify      | 36     | 0      | 2       | 0     | 38    | ✅     |
| Package     | 18     | 0      | 13      | 0     | 31    | ✅     |
| Monitor     | 8      | 0      | 0       | 0     | 8     | ✅     |
| Data Stores | 31     | 0      | 0       | 0     | 31    | ✅     |
| Release     | 5      | 0      | 0       | 0     | 5     | ✅     |
| Fulfillment | 1      | 0      | 0       | 0     | 1     | ✅     |
| Analytics   | 2      | 0      | 0       | 0     | 2     | ✅     |
| Manage      | 0      | 0      | 1       | 0     | 1     | ➖     |
+-------------+--------+--------+---------+-------+-------+--------+
| Total       | 352    | 0      | 29      | 0     | 381   | ✅     |
+-------------+--------+--------+---------+-------+-------+--------+

e2e-test-on-cng: test report for ee0a55ce

expand test summary

+------------------------------------------------------------------+
|                          suites summary                          |
+-------------+--------+--------+---------+-------+-------+--------+
|             | passed | failed | skipped | flaky | total | result |
+-------------+--------+--------+---------+-------+-------+--------+
| Govern      | 77     | 0      | 9       | 0     | 86    | ✅     |
| Growth      | 0      | 0      | 2       | 0     | 2     | ➖     |
| Create      | 135    | 0      | 15      | 0     | 150   | ✅     |
| Verify      | 53     | 0      | 13      | 0     | 66    | ✅     |
| Monitor     | 8      | 0      | 12      | 0     | 20    | ✅     |
| Package     | 22     | 0      | 16      | 0     | 38    | ✅     |
| Plan        | 78     | 1      | 11      | 0     | 90    | ❌     |
| Data Stores | 34     | 0      | 9       | 0     | 43    | ✅     |
| Release     | 5      | 0      | 1       | 0     | 6     | ✅     |
| Manage      | 2      | 0      | 8       | 0     | 10    | ✅     |
| Analytics   | 2      | 0      | 0       | 0     | 2     | ✅     |
| Fulfillment | 2      | 0      | 24      | 0     | 26    | ✅     |
| ModelOps    | 0      | 0      | 1       | 0     | 1     | ➖     |
| Configure   | 0      | 0      | 3       | 0     | 3     | ➖     |
| Ai-powered  | 0      | 0      | 1       | 0     | 1     | ➖     |
| Secure      | 3      | 0      | 2       | 0     | 5     | ✅     |
+-------------+--------+--------+---------+-------+-------+--------+
| Total       | 421    | 1      | 127     | 0     | 549   | ❌     |
+-------------+--------+--------+---------+-------+-------+--------+

approved this merge request

added pipelinetier-3 label and removed pipelinetier-2 label

resolved all threads

enabled automatic add to merge train when the pipeline for a036fd5f succeeds

added this merge request to the merge train at position 2