…nfiguration handling (#23)

This pull request introduces several significant changes to the
`GoogleSecrets` configuration functionality. The most important updates
include the addition of a new overload for `AddGoogleSecrets`, the
removal of redundant code, and enhancements to the handling of
`GoogleSecretsOptions`.

### Key Changes:

#### New Features:
* Added a new overload for `AddGoogleSecrets` to allow passing
`GoogleSecretsOptions`.

#### Code Simplification:
* Removed the redundant environment variable check for
`GoogleSecretsProject` in `ConfigurationBuilderExtensions`.
[[1]](diffhunk://#diff-3a42ad5a1b6e9fd57bf3513b6cdee8a15582556ed87bd3a456c3cff0da036c27L20-L29)
[[2]](diffhunk://#diff-4c1edd3a47fe0ee6052f244806defa0d9acf7a1e57660749e2a7de329850795eL20-R33)
* Simplified the `AddGoogleSecrets` method by removing the check for
`ProjectName` in `GoogleSecretsOptions`.

#### Enhancements:
* Set the `ProjectName` property in `GoogleSecretsOptions` to default to
the environment variable `GoogleSecretsProject` if available.
* Added a warning log and early return in `GoogleSecretsProvider` if
`ProjectName` is not set.

Introduce a log message to indicate which Google Secrets project is
being loaded, enhancing debugging capabilities when multiple projects
are in use.