Add support for more unary and binary operators.

In order to support setLaterBit and resetLaterBit in
BitSetArray::Iterator there were 2 choices -
1. Make a copy of BitSetArray only if it is a mutating usecase
2. Always perform a copy in the constructor

BitSetIteratorPerfTest was run with both patches -
    1) Copy only when necessary - RESULT BitSetIteratorPerf.wall_time: run = 116.1067374961 ns
    2) Copy always -              RESULT BitSetIteratorPerf.wall_time: run = 242.7446459439 ns

We settled on the copy only when necessary path.

Bug: angleproject:3877
Change-Id: If1d3cc428c68c84857952b46237aa5f206f080cd
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2690912
Commit-Queue: Mohan Maiya <m.maiya@samsung.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>