Adds support for camelCase credential property names

[zhangeugenia]

Description

Updates PnsCredential to invoke the correct setters when credential property names are returned in camelCase instead of PascalCase. When the properties are camelCase, the SDK attempts to invoke setters with a different casing when parsing NotificationHubDescriptions, resulting in various functions (such as getNotificationHub()) crashing.

Also:

• Marks camelCase variant of setgoogleApiKey as deprecated
• Updates JUnit to 5 to use ParameterizedTests

Things to consider before you submit the PR:

• Are tests passing locally?
• Are the files formatted correctly?
• Did you add unit tests?
• Did you test your change with either the sample apps that are included in the repository or with a blank app that uses your change?

Related PRs or issues

Reported in Issue #169