Support installation via .sdkmanrc

I'm interested in [Java (via SDKMan)](https://github.com/devcontainers/features/tree/main/src/java) but this will apply to any tool available via SDKMan. SDKMan supports installing tools if those are listed in `.sdkmanrc` file, see [the docs](https://sdkman.io/usage#env). So, if repositories contain `.sdkmanrc` with content `java=21-tem` then `sdk env install` will install Java 21 from Temurin vendor.