[CoreCLR] Remove DSO-cache hashes: decouple JNI preload and rework p/invoke fallback

[simonrozsival]

Context

After #12010 (p/invoke override rewritten to plain string comparisons) and #12033 (dlopen-based assembly store loading, which removes DSOApkEntry and the ZIP-scan fast path), the only remaining functional consumer of DSOCacheEntry.hash in the CoreCLR host is the p/invoke fallback lookup (MonodroidDl::find_dso_cache_entry, called once from monodroid_dlopen(name)).

JNI shared-library preloading (host.cc) uses the dso_cache array too, but it needs no hashes: it is driven by dso_jni_preloads_idx (a list of indexes) → DSOCacheEntry::name_index → name → System.loadLibrary. entry.hash appears there only as a log_debug argument, and entry.real_name_hash is only used by find_dso_apk_entry, which #12033 deletes.

In other words, preload and "resolve an arbitrary p/invoke library by name" are two unrelated concerns fused into one hash-indexed table; the hashes exist solely for the fallback lookup.

Blocked on

• [CoreCLR] Remove robin-map from p/invoke override #12010
• [CoreCLR] Experimental: dlopen()-based assembly store loading #12033

Both actively rewrite the same files (precompiled.cc, pinvoke-override*.hh, monodroid-dl.hh, the CLR app-config generator), so this cleanup should land on a stable base to avoid churn/conflicts.

Work

1. Decouple JNI preload into a standalone, hash-free list of names (generator side in ApplicationConfigNativeAssemblyGeneratorCLR.cs + the preload loop in host.cc). No dependency on DSOCacheEntry hash fields.
   • Note on handle sharing: today preload writes the loaded handle back into dso_cache (+ alias entries) so a later p/invoke reuses it. If decoupled, a preloaded lib later hit by p/invoke simply re-resolves via System.loadLibrary (idempotent → same handle, negligible cost). Correctness is preserved.
2. Rework/remove the p/invoke fallback lookup (monodroid_dlopen(name) → find_dso_cache_entry), aligned with the [CoreCLR] Remove robin-map from p/invoke override #12010 direction of letting CoreCLR's own resolver / System.loadLibrary handle arbitrary libraries.
3. Once (1) and (2) are done, dso_cache collapses to just preload names → drop DSOCacheEntry.hash / real_name_hash and remove CRC32 from the CoreCLR DSO path entirely.

Out of scope / note

#12013 ("[CoreCLR] Replace xxhash with crc32") deliberately only does the mechanical xxHash→CRC32 swap on the surviving fallback lookup. It does not attempt the decoupling or fallback rework above.