Stop checking for and writing out breadcrumbs for Microsoft.NET.DotNetHostPolicy

[elinor-fung]

This package hasn't been the way we construct .NET apps since before 3.0. We currently check for it in the deps.json on startup and write it out as a breadcrumb file for every app - we should be able to stop doing this and avoid some unnecessary file I/O and allocations.

cc @dotnet/appmodel @AaronRobinsonMSFT

[dotnet-policy-service]

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[Copilot]

Pull request overview

This PR removes legacy code for tracking and resolving the Microsoft.NETCore.DotNetHostPolicy package, which hasn't been used since before .NET 3.0. The changes eliminate unnecessary file I/O operations (breadcrumb writes and deps.json parsing) and simplify the hostpolicy resolution logic.

Key changes:

• Simplified breadcrumb setup in hostpolicy_context.cpp by removing explicit policy package tracking
• Removed deps.json parsing logic that searched for hostpolicy version information
• Streamlined hostpolicy_resolver::try_get_dir() signature by removing unused probe_paths parameter
• Removed obsolete package-related macros from configure.h.in

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/native/corehost/hostpolicy/hostpolicy_context.cpp	Simplified breadcrumb initialization by removing hardcoded hostpolicy package insertion and consolidating resolver call
src/native/corehost/fxr/standalone/hostpolicy_resolver.cpp	Removed legacy functions for parsing deps.json, probing package directories, and servicing lookups; simplified try_get_dir() to only check expected locations
src/native/corehost/fxr/hostpolicy_resolver.h	Updated try_get_dir() signature to remove probe_realpaths parameter
src/native/corehost/fxr/fx_muxer.cpp	Updated all try_get_dir() call sites to match new signature
src/native/corehost/configure.h.in	Removed HOST_POLICY_PKG_NAME and HOST_POLICY_PKG_REL_DIR macro definitions
src/native/corehost/apphost/static/hostpolicy_resolver.cpp	Updated try_get_dir() signature to match header
src/installer/tests/TestUtils/DotNetBuilder.cs	Removed test code that created mock DotNetHostPolicy package structure