Add unmanaged option to file proto

[aphralG]

Proposed changes

Add Unmanaged option to File proto

• When determining the file actions during a config apply, if unmanaged is set to true for a file the file will be treated as if it is unchanged, so that no action is performed on the file during a config apply.

// Represents meta data about a file
message File {
    // Meta information about the file, the name (including path) and hash
    FileMeta file_meta = 1;
    // Action enumeration
    enum FileAction {
        // Default value, no action
        FILE_ACTION_UNSPECIFIED = 0;
        // No changes to the file
        FILE_ACTION_UNCHANGED = 1;
        // New file
        FILE_ACTION_ADD = 2;
        // Updated file
        FILE_ACTION_UPDATE = 3;
        // File deleted
        FILE_ACTION_DELETE = 4;
    }
    // Optional action
    optional FileAction action = 2;
    // Unmanaged files will not be modified
    bool unmanaged = 3;
}

Checklist

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• I have read the CONTRIBUTING document
• I have run make install-tools and have attached any dependency changes to this pull request
• If applicable, I have added tests that prove my fix is effective or that my feature works
• If applicable, I have checked that any relevant tests pass after adding my changes
• If applicable, I have updated any relevant documentation (README.md)
• If applicable, I have tested my cross-platform changes on Ubuntu 22, Redhat 8, SUSE 15 and FreeBSD 13