[release] Prepare release coreunstable-1.14.0-beta.1 (#6690)

Co-authored-by: opentelemetrybot <107717825+opentelemetrybot@users.noreply.github.com>

Author: otelbot-dotnet[bot]

src/OpenTelemetry.Exporter.Prometheus.AspNetCore/CHANGELOG.md

@@ -7,6 +7,10 @@ Notes](../../RELEASENOTES.md).
 
 ## Unreleased
 
+## 1.14.0-beta.1
+
+Released 2025-Nov-12
+
 * **Breaking Change** When targeting `net8.0`, the package now depends on version
   `8.0.0` of the `Microsoft.Extensions.DependencyInjection.Abstractions`,
   `Microsoft.Extensions.Diagnostics.Abstractions` and

src/OpenTelemetry.Exporter.Prometheus.HttpListener/CHANGELOG.md

@@ -7,6 +7,10 @@ Notes](../../RELEASENOTES.md).
 
 ## Unreleased
 
+## 1.14.0-beta.1
+
+Released 2025-Nov-12
+
 * **Breaking Change** When targeting `net8.0`, the package now depends on version
   `8.0.0` of the `Microsoft.Extensions.DependencyInjection.Abstractions`,
   `Microsoft.Extensions.Diagnostics.Abstractions` and

src/OpenTelemetry.Shims.OpenTracing/CHANGELOG.md

@@ -6,6 +6,10 @@ Notes](../../RELEASENOTES.md).
 
 ## Unreleased
 
+## 1.14.0-beta.1
+
+Released 2025-Nov-12
+
 * Add support for .NET 10.0.
   ([#6307](https://github.com/open-telemetry/opentelemetry-dotnet/pull/6307))