Revert "Partially revert PR #125326: revert ComActivator/LicenseInter…

[AaronRobinsonMSFT]

…opProxy changes (#125706)"

This reverts commit 3e79783.

This commit also does the following:

• Fix test bug in LicenseTesting.h
• Rewrite BSTRHolder to a simpler form
• Remove layers in the managed site
• Use the BSTR marshaller instead of Marshal class helpers
• Remove unused signatures

Contributes to #123864

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[Copilot]

Pull request overview

This PR reverts a prior partial revert affecting COM licensing activation, and refactors the CoreCLR↔managed licensing glue to use the [UnmanagedCallersOnly] calling pattern and BSTR marshalling while also fixing a native test ownership bug.

Changes:

• Fix BSTR ownership in the COM native test server (LicenseTesting now copies the incoming license BSTR before freeing).
• Switch COM licensing activation in runtimecallablewrapper.cpp from MethodDescCallSite/manual ARG_SLOT plumbing to UnmanagedCallersOnlyCaller, updating the managed LicenseInteropProxy entrypoints accordingly.
• Introduce a simplified BSTRHolder RAII type in holder.h and remove the older utilcode.h typedef; remove some metasig entries and unused signatures.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/tests/Interop/COM/NativeServer/LicenseTesting.h	Fixes BSTR ownership by copying the incoming license string before destructor frees it.
src/tests/Interop/COM/NETClients/Licensing/Program.cs	Renames a helper to DesignTime and updates the corresponding logging/call sites.
src/coreclr/vm/runtimecallablewrapper.cpp	Reworks licensing activation to call managed helpers via UnmanagedCallersOnlyCaller and uses BSTRHolder.
src/coreclr/vm/metasig.h	Removes several COM-related metasig definitions and one duplicate RetObj signature entry.
src/coreclr/vm/interoputil.cpp	Updates BSTRHolder initialization style for a temporary BSTR allocation.
src/coreclr/vm/corelib.h	Changes LICENSE_INTEROP_PROXY binder method signatures to NoSig for UCO usage.
src/coreclr/utilcode/comex.cpp	Updates to default-constructed BSTRHolder usage for IErrorInfo::GetDescription.
src/coreclr/inc/utilcode.h	Removes the old util::BSTRHolder typedef and its helper free function.
src/coreclr/inc/holder.h	Adds a new BSTRHolder RAII class under FEATURE_COMINTEROP.
src/coreclr/System.Private.CoreLib/src/Internal/Runtime/InteropServices/ComActivator.cs	Adds [UnmanagedCallersOnly] entrypoints for LicenseInteropProxy and switches to BStrStringMarshaller for BSTR conversion.

[Copilot]

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated no new comments.

Comments suppressed due to low confidence (1)

src/tests/Interop/COM/NativeServer/LicenseTesting.h:35

• The constructor now allocates a new BSTR before checking s_DenyLicense, but if s_DenyLicense is true the constructor throws and the destructor won’t run, leaking the newly allocated _lic. Consider performing the deny check before allocating, or using a temporary holder/RAII (allocate into a local, then assign to _lic only after the throw path is ruled out).

    LicenseTesting(_In_opt_ BSTR lic)
        : _lic{ TP_SysAllocString(lic) }
    {
        if (s_DenyLicense)
            throw CLASS_E_NOTLICENSED;
    }