Update GenerateRuntimeConfigurationFiles task to generate Hot Reload runtime options

[tmat]

Update GenerateRuntimeConfigurationFiles task to generate Hot Reload runtime options to runtimeconfig.dev.json

The goal is to enable Hot Reload switches in all Debug builds, even if the project publishes AOT binaries.
We do so by generating runtimeconfig.dev.json, which overrides settings specified in runtimeconfig.json. The latter gets published while the former is only used for local development, thus the value of runtime switches of the published app can be different (Hot Reload disabled) than for dev builds (Hot Reload enabled).

This approach used to be blocked by dotnet/runtime#126606, which was recently fixed via
dotnet/runtime#128383. If the project targets .NET 10 or older the runtimeconfig.dev.json settings won't override runtimeconfig.json. We generate the dev.json file regardless as there is no harm to do so and it keeps the logic simpler.

See also discussion on dotnet/runtime#126546

Additionally, enable Hot Reload in dontet-watch when runtimeconfig.dev.json is generated with Hot Reload settings.

[github-actions]

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[Copilot]

Pull request overview

This PR updates the SDK’s runtimeconfig generation pipeline so runtimeconfig.dev.json can be generated for Hot Reload runtime switches (in addition to the existing probing-paths behavior), aligning with the Hot Reload runtime options requirements described in dotnet/runtime#126606.

Changes:

• Split GenerateRuntimeConfigurationFiles dev-config generation into two independent switches: probing paths vs Hot Reload runtime options.
• Update Microsoft.NET.Sdk.targets to compute GenerateRuntimeConfigDevFile based on the new switches and pass the new parameters to the task.
• Add unit tests validating runtimeconfig.dev.json contents for Hot Reload-only, probing-paths-only, both enabled, and both disabled scenarios.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
test/Microsoft.NET.Build.Tasks.Tests/GivenAGenerateRuntimeConfigMultiThreading.cs	Adds coverage for Hot Reload runtime options emission into runtimeconfig.dev.json under different switch combinations.
src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.Sdk.targets	Introduces new MSBuild properties for dev-config generation and wires them into the GenerateRuntimeConfigurationFiles task invocation.
src/Tasks/Microsoft.NET.Build.Tasks/GenerateRuntimeConfigurationFiles.cs	Implements Hot Reload runtime switch emission into runtimeconfig.dev.json and gates probing-path generation behind a dedicated switch.