Seed generation passes when experiment name is duplicated

[btlechowski]

The generation seed job should fail, but it passes.

Then in the client the seed is not applied:

[27107:259:1109/120010.074659:VERBOSE1:processed_study.cc(98)] BraveSearchAdStudy has a repeated experiment name Enabled

cc @atuchin-m @tmancey @iambrianfung

[tmancey]

Raised #817 to fix the issue for now. But would be great to detect during seed generation

[btlechowski]

seed that failed:

        {
            "experiments": [
                {
                    "feature_association": {
                        "enable_feature": [
                            "ShouldAlwaysRunBraveAdsService",
                            "ShouldSupportSearchResultAds",
                            "ShouldAlwaysTriggerBraveSearchResultAdEvents"
                        ]
                    },
                    "name": "Enabled",
                    "probability_weight": 100
                    "probability_weight": 90
                },
                {
                    "feature_association": {
                        "enable_feature": [
                            "ShouldLaunchBraveAdsAsInProcessService",
                            "ShouldAlwaysRunBraveAdsService",
                            "ShouldSupportSearchResultAds",
                            "ShouldAlwaysTriggerBraveSearchResultAdEvents"
                        ]
                    },
                    "name": "Enabled",
                    "probability_weight": 10
                },
                {
                    "name": "Default",
                    "probability_weight": 0
                }
            ],
            "filter": {
                "channel": [
                    "RELEASE"
                ],
                "platform": [
                    "WINDOWS",
                    "MAC",
                    "LINUX",
                    "ANDROID"
                ]
            },
            "name": "BraveSearchAdStudy"
        },

experiment name is duplicated:

"name": "Enabled",