Switch from JwtSecurityToken and JwtTokenValidators to JsonWebToken and TokenHandler in .NET 8

[laura-rodriguez]

Describe the feature request?

There's a more optimal way to validate tokens described here.

Currently, we're using options.UseSecurityTokenValidators = true, but we want this library to comply with .NET 8 fully.

.NET Version

.NET 8

Additional Information?

Internal Ref: OKTA-720772
#262 (comment)