HybridCache: add net10 HybridCache zero-alloc fetch API

[mgravell]

implements span/DISH API for HybridCache as proposed in #112866 and agreed at API review, 2025-04-08

Concrete implementation (i.e. an override) will be added over in dotnet/extensions

[dotnet-issue-labeler]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

[dotnet-issue-labeler]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

[Copilot]

Copilot reviewed 3 out of 4 changed files in this pull request and generated no comments.

Files not reviewed (1)

• src/libraries/Microsoft.Extensions.Caching.Abstractions/ref/Microsoft.Extensions.Caching.Abstractions.csproj: Language not supported

[dotnet-policy-service]

Tagging subscribers to this area: @dotnet/area-extensions-caching
See info in area-owners.md if you want to be subscribed.