feat: namespace migration for settings

[joerivanveen]

This namespace migration was created during the rework to get the proposition from the api key. It was decided not to rename the module because that would require an uninsstall + reinstall into PrestaShop, which enforces the name of the module to be the same as the folder and the initial class php file.
Here it is stored for use with a later major release that will rename the module to align more with the names in other plugins.

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
110	1	109	4

View the top 1 failed test(s) by shortest run time

Tests.Unit.UpgradeTest::it runs upgrade with (invalid) old api key saved

Stack Traces | 0.0718s run time

.../tests/Unit/UpgradeTest.php::it runs upgrade with (invalid) old api key saved
Failed asserting that two arrays are equal.
--- Expected
+++ Actual
@@ @@
 Array (
-    'message' => '[PDK]: Existing API key is invalid'
+    'message' => '[PDK]: Failed to run namespace migration'
 )

.../pest/src/Expectation.php:497
.../pdk/tests/Pest.php:37
.../src/Concerns/Extendable.php:52
.../pest/src/Expectation.php:972
.../tests/Unit/UpgradeTest.php:80
.../src/Factories/TestCaseFactory.php:151
.../src/Concerns/Testable.php:301
.../src/Support/ExceptionTrace.php:29
.../src/Concerns/Testable.php:302
.../src/Concerns/Testable.php:278
.../src/Console/Command.php:119
.../pest/bin/pest:61
.../pest/bin/pest:62

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