Extend contract set change alerts with host info

[peterjan]

This PR adds host info to the contract set change alert, as requested in #963

REQUIRES UI CHANGE
This PR requires an accompanying UI change to ensure the alert is displayed properly. I'm wondering whether we should create a list of alerts + properties in the frontend, and only display those keys and alerts. That way we could always maintain backwards compatibility in the backend, but tweak or add alerts. We can merge that separately from the frontend and then when the frontend made the required changes we can get rid of the redundant/old compat code we had to add. Downside would be that every new alert or added property would need a UI update to get displayed.

Example screenshot:

Example JSON:

{
		"id": "h:f27b88af9f84c7b51121b902d91c7ec5b0d557470f6f9a9b871c333101b1bace",
		"severity": "info",
		"message": "Contract set changed",
		"data": {
			"added": 2,
			"hint": "A high churn rate can lead to a lot of unnecessary migrations, it might be necessary to tweak your configuration depending on the reason hosts are being discarded from the set.",
			"name": "autopilot",
			"origin": "autopilot.autopilot",
			"removals": {
				"fcid:0d3e929712f5787f50088f407628e53c821afa6eb2168488f42b680a40dfb528": "truncated",
				"fcid:dbfdbf6889bc164af52111639cce4eb2a36195dea4ed0df64d25dc67f107a185": "truncated"
			},
			"removed": 2,
			"set": {
				"fcid:1e47af48a39193a2daa5b3353d69d11ec8461de0a8046c3a4ee4d6962e3d6e30": "ed25519:87e90594ac909076f6473fbebfe278fa6794fe0bb7b3b093b0792e5a5b734239",
				"fcid:483e0596f9a4c838be9eb3510db47f9e8dc3a694cc6533a495ea407c5521f50a": "ed25519:b078bef7e2ea7a9e1d0594658b75ad4f40fc2abd3f2ab86048a0ac54747c2b9e",
				"fcid:7f16d77da8e4cb061e03ba3c763344545f11edd8b53a55c1f119870091a754dd": "ed25519:96bf3099f428f3affe45dcb30b904e5f4f3f33da368d9316d32b4fe0e4bec223",
				"fcid:85401e621970d3d1b1a272214bb80aaf6cc86dc2e2e004a658ecd42a7221e20f": "ed25519:80878e4094555a7af2fd7155903e3fc149dcff650d01544c9685ad6cb799a620",
				"fcid:96e7d7ddc60b16fca0c7aeff991bc05fbbd2f3e497364348a82f73226c9fd8cb": "ed25519:95770d3b9bf02e025bb7f76715cccf943974e73c480d81e1d9b480845bca1989",
				"fcid:985087e5c165fb0e76112b456744e4a424dc111b6faabbc2d63fceb57e6ad236": "ed25519:075c746dd0e85eea7aeb05a5c4f37c2af35e4a8c48493fccec285ead4dbe5c49",
				"fcid:b0ffea63cf1509b1a98a9e7e78d182e2664b5ddeb6167d50508f2819ab393a3c": "ed25519:a3aef7db34413e0f1d33140c3cab0a0113317d55b99df6c77a38fbc7a11d2ae1",
				"fcid:c40207017ccce23cef4cdfacf1d40e793c61d73b7108d1e05188131a9c29f60c": "ed25519:66aa6e0a08073250d01cadf997fa568b02646a873d0b319e6a6308fd12ba07ef",
				"fcid:c7a18551ef3e802333e1bed810efafa3ae66d053d4e01e11f1d2d725d1d6ccf5": "ed25519:22eecdbd45e8a445adea8584934aeaa74d54898bb111439556a0a2cb9bdce13d",
				"fcid:ce9f9509da2e632f371861d85a4ff0218dcd4070e9e109187be0b953adc4182f": "ed25519:9d0dc5d8a28332254debcf81c83ba429283293cc9647f96cd1071dad34717aab",
				"fcid:de83db92f43de9dad4f17b93bc0c674921fb75af6d5817b7cce504fc289db3e9": "ed25519:c101ca41273de728bd51c76c003c2d9ff93cba713c2c57850c5e50a66a7a8791",
				"fcid:e5918ca79f78206be0c9adb0ceabc0d1ed21f6c026286d41102f2a7e43132d02": "ed25519:707d189dfd08469efebf1a51338b3d73eed4ac1b56213a0ed6521179f60a7b71"
			},
			"set_additions": {
				"fcid:1e47af48a39193a2daa5b3353d69d11ec8461de0a8046c3a4ee4d6962e3d6e30": {
					"hostKey": "ed25519:87e90594ac909076f6473fbebfe278fa6794fe0bb7b3b093b0792e5a5b734239",
					"size": 0
				},
				"fcid:985087e5c165fb0e76112b456744e4a424dc111b6faabbc2d63fceb57e6ad236": {
					"hostKey": "ed25519:075c746dd0e85eea7aeb05a5c4f37c2af35e4a8c48493fccec285ead4dbe5c49",
					"size": 0
				}
			},
			"set_removals": {
				"fcid:0d3e929712f5787f50088f407628e53c821afa6eb2168488f42b680a40dfb528": {
					"hostKey": "ed25519:09a5972a8fe871f765a52729fab15a78a2e0a7d85a8b614de3f4295f2a87292b",
					"reason": "truncated",
					"size": 0
				},
				"fcid:dbfdbf6889bc164af52111639cce4eb2a36195dea4ed0df64d25dc67f107a185": {
					"hostKey": "ed25519:34d5b8b744c61689df3a67120975109495abf2306dd8228275a8378f97649cb1",
					"reason": "truncated",
					"size": 0
				}
			}
		},
		"timestamp": "2024-02-15T09:29:23.06047+01:00"
	}