Add GraphOptimizer to Grappler item builder to do L1 optimizations and

inlining.

Op Counts Comparison (BNMT)
Counts: Profile vs Grappler
Op: Add, 968 vs 965
Op: AddN, 2228 vs 2228
Op: ApplyGradientDescent, 84 vs 84
Op: BatchMatMul, 998 vs 998
Op: Identity, 142 vs 105
Op: MatMul, 63 vs 63
Op: Mul, 10318 vs 10306
Op: OneHot, 1 vs 1
Op: Reshape, 8421 vs 8422
Op: Select, 488 vs 488
Op: Shape, 8132 vs 8131
Op: Sigmoid, 942 vs 942
Op: Softmax, 19 vs 19
Op: StridedSlice, 58 vs 74
Op: Sub, 1398 vs 1394
Op: Tanh, 333 vs 333
Op: Tile, 21 vs 21
Op: Transpose, 39 vs 39
PiperOrigin-RevId: 157288420