FACT-1874 - Adds Private Law secrets to demo

[RuthKirby]

Jira link (if applicable)

https://tools.hmcts.net/jira/browse/FACT-1874

Change description

Adds Private Law secrets to demo for testing.

Checklist

• [ ] commit messages are meaningful and follow good commit message guidelines
• [ ] README and other documentation has been updated / added (if needed)
• [ ] tests have been updated / new tests has been added (if needed)
• [ ] Does this PR introduce a breaking change

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apps/bsp/bulk-scan-payment-processor/demo.yaml

• Added keyVaults section with various secrets and aliases for the bulk-scan key vault.