Make sure OidcRequestContextProperties are always modifiable

[sberyozkin]

This is a follow up to #44203, which was not complete because Map.of can be passed to OidcRequestContextProperties from different locations, the test in #44203 works because it just happens that a modifiable map is passed to OidcRequestContextProperties during the token request, with test filters which modify properties being bound to the token request.

Thanks to @sschellh for noticing it.

[sberyozkin]

Thanks @gastaldi, let me check that flaky test

[sberyozkin]

@gastaldi The test failure is not related but I just added 2 extra secs there to minimize flakiness

[quarkus-bot]

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