Revert "Reland "Create a basic IRNode pooling system.""

This reverts commit 5b09e6a00788d08a89604bd77f154c0e11dda035.

Reason for revert: breaking g3

Original change's description:
> Reland "Create a basic IRNode pooling system."
>
> This is a reland of e16eca95f5c08c2bdf72cc0b04af62a1071afd8d
>
> Original change's description:
> > Create a basic IRNode pooling system.
> >
> > Allocations are redirected by overriding `operator new` and `operator
> > delete` on the IRNode class. This allows us to use our existing
> > `unique_ptr` and `make_unique` calls as-is. The Pool class is simple;
> > it holds a fixed number of nodes and recycles them as they are returned.
> >
> > A fixed pool size of 2000 nodes was chosen. That is large enough to hold
> > the contents of `sksl_large` during compilation, but it can be
> > overflowed by very large shaders, or if multiple programs are converted
> > at the same time. Exhausting the pool is not a problem; if this happens,
> > additional nodes will be allocated via the system allocator as usual.
> > More elaborate schemes are possible but might not add a lot of value.
> >
> > Thread safety is accomplished by placing the pool in a `thread_local`
> > static during a Program's creation and destruction; the pool is freed
> > when the program is destroyed. One important consequence of this
> > strategy is that a program must free every node that it allocated during
> > its creation, or else the node will be leaked. In debug, leaking a node
> > will be detected and causes a DEBUGFAIL. In release, the pool will be
> > freed despite having a live node in it, and if that node is later freed,
> > that pointer will be passed to the system `free` (which is likely to
> > cause a crash).
> >
> > In this CL, iOS does not support pooling, since support for
> > `thread_local` was only added on iOS 9. This is fixed in the followup
> > CL, http://review.skia.org/328837, which uses pthread keys on iOS.
> >
> > Nanobench shows ~15% improvement:
> >   (last week) http://screen/5CNBhTaZApcDA8h
> >       (today) http://screen/8ti5Rymvf6LUs8i
> >
> > Change-Id: I559de73606ee1be54e5eae7f82129dc928a63e3c
> > Reviewed-on: https://skia-review.googlesource.com/c/skia/+/326876
> > Commit-Queue: John Stiles <johnstiles@google.com>
> > Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
> > Auto-Submit: John Stiles <johnstiles@google.com>
>
> Change-Id: I114971e8e7ac0fabaf26216ae8813eeeaad0d4a2
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/329086
> Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
> Commit-Queue: John Stiles <johnstiles@google.com>

TBR=brianosman@google.com,ethannicholas@google.com,johnstiles@google.com

Change-Id: Ie77a23366f2ba52fcbb0a751d11ca2792790a30c
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/329165
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
6 files changed