[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, 8 insertions, 22 deletions

diff --git a/src/installer/corehost/cli/hostmisc/pal.unix.cpp b/src/installer/corehost/cli/hostmisc/pal.unix.cpp
index 3626761b0ec..2ca39c3793a 100644
--- a/src/installer/corehost/cli/hostmisc/pal.unix.cpp
+++ b/src/installer/corehost/cli/hostmisc/pal.unix.cpp
@@ -70,7 +70,7 @@ bool pal::touch_file(const pal::string_t& path)
     return true;
 }
 
-static void* map_file(const pal::string_t& path, size_t* length, int prot, int flags)
+void* pal::map_file_readonly(const pal::string_t& path, size_t& length)
 {
     int fd = open(path.c_str(), O_RDONLY);
     if (fd == -1)
@@ -86,35 +86,21 @@ static void* map_file(const pal::string_t& path, size_t* length, int prot, int f
         close(fd);
         return nullptr;
     }
-    size_t size = buf.st_size;
 
-    if (length != nullptr)
-    {
-        *length = size;
-    }
-
-    void* address = mmap(nullptr, size, prot, flags, fd, 0);
+    length = buf.st_size;
+    void* address = mmap(nullptr, length, PROT_READ, MAP_SHARED, fd, 0);
 
-    if (address == MAP_FAILED)
+    if(address == nullptr)
     {
         trace::error(_X("Failed to map file. mmap(%s) failed with error %d"), path.c_str(), errno);
-        address = nullptr;
+        close(fd);
+        return nullptr;
     }
 
     close(fd);
     return address;
 }
 
-const void* pal::mmap_read(const string_t& path, size_t* length)
-{
-    return map_file(path, length, PROT_READ, MAP_SHARED);
-}
-
-void* pal::mmap_copy_on_write(const string_t& path, size_t* length)
-{
-    return map_file(path, length, PROT_READ | PROT_WRITE, MAP_PRIVATE);
-}
-
 bool pal::getcwd(pal::string_t* recv)
 {
     recv->clear();
@@ -504,10 +490,10 @@ bool pal::get_default_installation_dir(pal::string_t* recv)
 pal::string_t trim_quotes(pal::string_t stringToCleanup)
 {
     pal::char_t quote_array[2] = {'\"', '\''};
-    for (size_t index = 0; index < sizeof(quote_array)/sizeof(quote_array[0]); index++)
+    for(size_t index = 0; index < sizeof(quote_array)/sizeof(quote_array[0]); index++)
     {
         size_t pos = stringToCleanup.find(quote_array[index]);
-        while (pos != std::string::npos)
+        while(pos != std::string::npos)
         {
             stringToCleanup = stringToCleanup.erase(pos, 1);
             pos = stringToCleanup.find(quote_array[index]);