nir/range-analysis: Rudimentary value range analysis pass

Most integer operations are omitted because dealing with integer
overflow is hard.  There are a few things that could be smarter if there
was a small amount more tracking of ranges of integer types (i.e.,
operands are Boolean, operand values fit in 16 bits, etc.).

The changes to nir_search_helpers.h are included in this patch to
simplify reordering the changes to nir_opt_algebraic.py.

v2: Memoize range analysis results.  Without this, some shaders appear
to get stuck in infinite loops.

v3: Rebase on many months of Mesa changes, including 1-bit Boolean
changes.

v4: Rebase on "nir: Drop imov/fmov in favor of one mov instruction".

v5: Use nir_alu_srcs_equal for detecting (a*a).  Previously just the SSA
value was compared, and this incorrectly matched (a.x*a.y).

v6: Many code improvements including (but not limited to) better names,
more comments, and better use of helper functions.  All suggested by
Caio.  Rework the handling of several opcodes to use a table for mapping
source ranges to a result range.  This change fixed a bug that caused
fmax(gt_zero, ge_zero) to be incorrectly recognized as ge_zero.
Slightly tighten the range of fmul by recognizing that x*x is gt_zero if
x is gt_zero.  Add similar handling for -x*x.

v7: Use _______ in the tables as an alias for unknown.  Suggested by
Caio.

Reviewed-by: Caio Marcelo de Oliveira Filho <[email protected]>

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