Currently, `DIContext::getLineInfoForAddress` and
`DIContext::getLineInfoForDataAddress` returns empty DILineInfo when the
debug info is missing for the given address. This is not differentiable
with the case when debug info is found for the given address but the
debug info is default value (filename:linenum is <invalid>:0).

This change wraps the return types of `DIContext::getLineInfoForAddress`
and `DIContext::getLineInfoForDataAddress` with `std::optional`.

`Sym.getSection()` is equivalent to `Sym.getBlock().getSection()`.

Use SymbolStringPtr for Symbol names in LinkGraph. This reduces string interning
on the boundary between JITLink and ORC, and allows pointer comparisons (rather
than string comparisons) between Symbol names. This should improve the
performance and readability of code that bridges between JITLink and ORC (e.g.
ObjectLinkingLayer and ObjectLinkingLayer::Plugins).

To enable use of SymbolStringPtr a std::shared_ptr<SymbolStringPool> is added to
LinkGraph and threaded through to its construction sites in LLVM and Bolt. All
LinkGraphs that are to have symbol names compared by pointer equality must point
to the same SymbolStringPool instance, which in ORC sessions should be the pool
attached to the ExecutionSession.
---------

Co-authored-by: Lang Hames <lhames@gmail.com>

[ORC] Re-land https://github.com/llvm/llvm-project/pull/81826

This patch adds two plugins: VTuneSupportPlugin.cpp and
JITLoaderVTune.cpp. The testing is done in a manner similar to
llvm-jitlistener. Currently, we only support the old version of Intel
VTune API.

This reverts commit 17efdad2296a2757813e4f11d0575ee6fb826e39. It introduces a layering violation: https://github.com/llvm/llvm-project/pull/81826#issuecomment-1977455140

This patch adds two plugins: VTuneSupportPlugin.cpp and
JITLoaderVTune.cpp. The testing is done in a manner similar to
llvm-jitlistener. Currently, we only support the old version of Intel
VTune API.

This pull request is stacked on top of
https://github.com/llvm/llvm-project/pull/81825