Add release notes for .NET Provider 8.0.0 stable release (#975)

* release notes in progress, add 8.0.0 entries

* add mention of experimentation

* change title of section

* PR revisions

* update summary for variant flags

* update FM to say version 4

* PR comments

* PR comments

releaseNotes/MicrosoftAzureAppConfigurationAspNetCore.md

@@ -1,6 +1,9 @@
 # Microsoft.Azure.AppConfiguration.AspNetCore
 [Source code][source_code] | [Package (NuGet)][package]
 
+## 8.0.0 - October 3rd, 2024
+* Updated `Microsoft.Extensions.Configuration.AzureAppConfiguration` reference to `8.0.0`. See the [release notes](./MicrosoftExtensionsConfigurationAzureAppConfiguration.md) for more information on the changes.
+
 ## 8.0.0-preview.3 - July 18th, 2024
 * Updated `Microsoft.Extensions.Configuration.AzureAppConfiguration` reference to `8.3.0-preview.3`. See the [release notes](./MicrosoftExtensionsConfigurationAzureAppConfiguration.md) for more information on the changes.
 

releaseNotes/MicrosoftAzureAppConfigurationFunctionsWorker.md

@@ -1,6 +1,9 @@
 # Microsoft.Azure.AppConfiguration.Functions.Worker
 [Source code][source_code] | [Package (NuGet)][package]
 
+## 8.0.0 - October 3rd, 2024
+* Updated `Microsoft.Extensions.Configuration.AzureAppConfiguration` reference to `8.0.0`. See the [release notes](./MicrosoftExtensionsConfigurationAzureAppConfiguration.md) for more information on the changes.
+
 ## 8.0.0-preview.3 - July 18th, 2024
 * Updated `Microsoft.Extensions.Configuration.AzureAppConfiguration` reference to `8.3.0-preview.3`. See the [release notes](./MicrosoftExtensionsConfigurationAzureAppConfiguration.md) for more information on the changes.
 

releaseNotes/MicrosoftExtensionsConfigurationAzureAppConfiguration.md

@@ -1,6 +1,23 @@
 # Microsoft.Extensions.Configuration.AzureAppConfiguration
 [Source code][source_code] | [Package (NuGet)][package]
 
+## 8.0.0 - October 3rd, 2024
+### Breaking Changes
+* Increased the default maximum retry count when resolving Key Vault references and increased the minimum refresh interval to 1 minute. This helps prevent requests to Key Vault from being throttled and will reduce the chance of failing to resolve a secret due to momentary failures. [#589](https://github.com/Azure/AppConfiguration-DotnetProvider/issues/589)
+* Removed .NET 7 as a target framework as .NET 7 is out of support. [#567](https://github.com/Azure/AppConfiguration-DotnetProvider/pull/567)
+* The APIs `AzureAppConfigurationRefreshOptions.SetCacheExpiration` and `FeatureFlagOptions.CacheExpirationInterval` have been deprecated and will be removed in a future release. They are replaced with `AzureAppConfigurationRefreshOptions.SetRefreshInterval` and `FeatureFlagOptions.SetRefreshInterval`, respectively. This change does not affect functionality but aims to eliminate confusion regarding cache expiration implied by the previous API names. [#350](https://github.com/Azure/AppConfiguration-DotnetProvider/issues/350)
+
+### Enhancements
+* **Variant Feature Flags and Telemetry**: This is the first stable release with support for the `variants`, `allocation`, and `telemetry` properties for feature flags added by version 4.0.0 of the [Microsoft.FeatureManagement.*](https://github.com/microsoft/FeatureManagement-Dotnet) libraries. While variant feature flags can still be toggled on or off, they also allow for different configurations, ranging from simple primitives to complex JSON objects. Variant feature flags are particularly useful for feature rollouts, configuration rollouts, and feature experimentation (also known as A/B testing).
+* This is the first stable release of the load balancing mode introduced in 8.0.0-preview.3. Load balancing enables your application to distribute requests to App Configuration across all available replicas. This enhancement improves the scalability of applications that typically experience high request volumes to App Configuration, ensuring they remain within quota limits. Load balancing mode is off by default and can be activated by setting the new `AzureAppConfigurationOptions.LoadBalancingEnabled` property to `true`. [#535](https://github.com/Azure/AppConfiguration-DotnetProvider/pull/535)
+* Added the ability to configure options used to connect to Key Vault resources that have no registered `SecretClient` with the following new API. [#274](https://github.com/Azure/AppConfiguration-DotnetProvider/issues/274)
+
+   ```cs
+   public AzureAppConfigurationKeyVaultOptions ConfigureClientOptions(Action<SecretClientOptions> configure)
+   ```
+
+   This API can be called from within the `AzureAppConfigurationOptions.ConfigureKeyVault` method.
+
 ## 8.0.0-preview.3 - July 18th, 2024
 ### Breaking Changes
 * Removed .NET 7 as a target framework as .NET 7 is out of support. [#567](https://github.com/Azure/AppConfiguration-DotnetProvider/pull/567)