RFR: 8268129: LibraryLookup::ofDefault leaks symbols from loaded libraries [v6]

[Maurizio Cimadamore]

> This patch overhauls the library loading mechanism used by the Foreign Linker API. We realized that, while handy, the *default* lookup abstraction (`LibraryLookup::ofDefault`) was behaving inconsistentlt across platforms.
> 
> This patch replaces `LibraryLookup` with a simpler `SymbolLookup` abstraction, a functional interface. Crucially, `SymbolLookup` does not concern with library loading, only symbol lookup. For this reason, two factories are added:
> 
> * `SymbolLookup::loaderLookup` - which obtains a lookup that can be used to lookup symbols in libraries loaded by current loader
> * `CLinker::systemLookup` - a more stable replacement for the *default* lookup, which looks for symbols in libc.so (or its equivalent in other platforms). The contents of this lookup are unspecified.
> 
> Both factories are *restricted*, so they can only be called when `--enable-native-access` is set.

Maurizio Cimadamore has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 16 commits:

 - Merge branch 'master' into symbolLookup
 - Forgot to add makefile for building shim library
 - Address review comments
 - Update test/jdk/java/foreign/TestIntrinsics.java
   
   Co-authored-by: Paul Sandoz <paul.d.sandoz at googlemail.com>
 - Update test/jdk/java/foreign/valist/VaListTest.java
   
   Co-authored-by: Paul Sandoz <paul.d.sandoz at googlemail.com>
 - Update test/jdk/java/foreign/TestVarArgs.java
   
   Co-authored-by: Paul Sandoz <paul.d.sandoz at googlemail.com>
 - Update test/jdk/java/foreign/TestUpcall.java
   
   Co-authored-by: Paul Sandoz <paul.d.sandoz at googlemail.com>
 - Update test/jdk/java/foreign/TestIllegalLink.java
   
   Co-authored-by: Paul Sandoz <paul.d.sandoz at googlemail.com>
 - Update test/jdk/java/foreign/TestSymbolLookup.java
   
   Co-authored-by: Paul Sandoz <paul.d.sandoz at googlemail.com>
 - Update test/jdk/java/foreign/TestDowncall.java
   
   Co-authored-by: Paul Sandoz <paul.d.sandoz at googlemail.com>
 - ... and 6 more: https://git.openjdk.java.net/jdk/compare/52d8215a...2545e2b6

-------------

Changes: https://git.openjdk.java.net/jdk/pull/4316/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4316&range=05
  Stats: 1351 lines in 47 files changed: 626 ins; 621 del; 104 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4316.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4316/head:pull/4316

PR: https://git.openjdk.java.net/jdk/pull/4316