[release/5.0-preview4] Revert processing bundles in framework (#35679)v5.0.0-preview.4.20251.6

This commit reverts:
Revert "Single-File: Process bundles in the framework (#34274)"
This reverts commit 78b303df8fbb242985d049a277d0d199cafd51b5.

Revert "Single-File Bundler: Add a FileSize test (#35149)"
This reverts commit 779588a509b81d909ac5d496c172949ec1f1ddcc.

*Customer Scenario*

Publishing apps as a self-contained single-file doesn't work as expected.

* Publish needs to generate hostpolicy and hostfxr separate from the single file bundle
* Cross-platform publishing is incorrect

*Problem*

Since Static-apphost is not yet ready, processing bundle content in hostpolicy means that  hostpolicy and hostfxr DLLs need to be separate from the bundle. This causes self-contained single-file apps to not be a "single file" temporarily. 

The change also requires supporting changes from the SDK, to publish hostfxr and hostpolicy as separate files, and to invoke HostModel library with arguments that facilitate cross-platform publishing.

*Solution*

To solve these, problem, this change reverts:

Revert "Single-File: Process bundles in the framework (#34274)" commit 78b303df8fbb242985d049a277d0d199cafd51b5.

and a dependent test-only change:

Revert "Single-File Bundler: Add a FileSize test (#35149)" commit 779588a509b81d909ac5d496c172949ec1f1ddcc.

*Risk*

Medium
The change is contained to only host components: apphost, hostpolicy, and hostfxr.
However, the change is big, and needs testing in runtime and SDK repos.

*Testing*

Manually tested the SDK by inserting apphost, hostfxr, hostpolicy, and hostmodel library from this build into the `dotnet/packs` preview-4 SDK from https://github.com/dotnet/sdk/pull/11518 build.

Verified that:
* Singlefile apps can be published and run OK for  { Windows, Linux, Osx } x {netcoreapp3.0, netcoreapp3.1, netcoreapp5.0} 
* Cross-targeting builds of single-file apps build and run OK (ex: built on Windos, run on Mac).

1 files changed, 0 insertions, 8 deletions

diff --git a/src/installer/corehost/cli/fxr/fx_muxer.cpp b/src/installer/corehost/cli/fxr/fx_muxer.cpp
index 31c8c177978..00584e4a91e 100644
--- a/src/installer/corehost/cli/fxr/fx_muxer.cpp
+++ b/src/installer/corehost/cli/fxr/fx_muxer.cpp
@@ -27,7 +27,6 @@
 #include "sdk_info.h"
 #include "sdk_resolver.h"
 #include "roll_fwd_on_no_candidate_fx_option.h"
-#include "bundle/info.h"
 
 namespace
 {
@@ -263,7 +262,6 @@ namespace
         pal::string_t& runtime_config,
         const runtime_config_t::settings_t& override_settings)
     {
-        // Check for the runtimeconfig.json file specified at the command line
         if (!runtime_config.empty() && !pal::realpath(&runtime_config))
         {
             trace::error(_X("The specified runtimeconfig.json [%s] does not exist"), runtime_config.c_str());
@@ -295,11 +293,6 @@ namespace
 
     host_mode_t detect_operating_mode(const host_startup_info_t& host_info)
     {
-        if (bundle::info_t::is_single_file_bundle())
-        {
-            return host_mode_t::apphost;
-        }
-
         if (coreclr_exists_in_dir(host_info.dotnet_root))
         {
             // Detect between standalone apphost or legacy split mode (specifying --depsfile and --runtimeconfig)
@@ -364,7 +357,6 @@ namespace
     {
         pal::string_t runtime_config = command_line::get_option_value(opts, known_options::runtime_config, _X(""));
 
-        // This check is for --depsfile option, which must be an actual file.
         pal::string_t deps_file = command_line::get_option_value(opts, known_options::deps_file, _X(""));
         if (!deps_file.empty() && !pal::realpath(&deps_file))
         {