cmd/compile: remove chunking of rewrite rules

cmd/compile: remove chunking of rewrite rules

We added chunking of rewrite rules to speed up compiling package SSA.
This series of changes has significantly shrunk the number of
rewrite rules, and they are no longer being added nearly as fast.
Now that we are sharing v.Args across multiple rewrite rules,
there is additional benefit to having more rules in a single function.
Removing chunking now has an incidental impact on compiling package SSA,
marginally speeds up other compilation, shrinks the cmd/compile binary,
and simplifies the code.

name        old time/op       new time/op       delta
Template          211ms ± 2%        210ms ± 2%  -0.50%  (p=0.000 n=91+97)
Unicode          81.9ms ± 3%       81.8ms ± 3%    ~     (p=0.179 n=96+91)
GoTypes           731ms ± 2%        731ms ± 1%    ~     (p=0.442 n=94+96)
Compiler          3.43s ± 2%        3.41s ± 2%  -0.36%  (p=0.001 n=98+94)
SSA               8.30s ± 2%        8.32s ± 2%  +0.19%  (p=0.034 n=94+95)
Flate             135ms ± 2%        134ms ± 1%  -0.30%  (p=0.006 n=98+94)
GoParser          167ms ± 1%        167ms ± 1%  -0.22%  (p=0.001 n=92+94)
Reflect           453ms ± 2%        453ms ± 3%    ~     (p=0.306 n=98+97)
Tar               184ms ± 2%        183ms ± 2%  -0.31%  (p=0.012 n=94+94)
XML               249ms ± 2%        248ms ± 1%  -0.26%  (p=0.002 n=96+92)
[Geo mean]        419ms             418ms       -0.21%

name        old user-time/op  new user-time/op  delta
Template          273ms ± 2%        272ms ± 2%  -0.46%  (p=0.000 n=93+96)
Unicode           116ms ± 4%        117ms ± 4%    ~     (p=0.433 n=98+98)
GoTypes           977ms ± 2%        977ms ± 1%    ~     (p=0.971 n=92+99)
Compiler          4.56s ± 6%        4.53s ± 6%    ~     (p=0.081 n=100+100)
SSA               11.1s ± 2%        11.1s ± 2%    ~     (p=0.064 n=99+96)
Flate             167ms ± 2%        167ms ± 1%  -0.24%  (p=0.004 n=95+96)
GoParser          203ms ± 1%        203ms ± 2%  -0.14%  (p=0.049 n=96+97)
Reflect           595ms ± 2%        595ms ± 2%    ~     (p=0.544 n=95+92)
Tar               225ms ± 2%        224ms ± 2%    ~     (p=0.562 n=99+99)
XML               312ms ± 2%        311ms ± 1%    ~     (p=0.050 n=97+93)
[Geo mean]        543ms             542ms       -0.13%

Change-Id: I8d34ab59f154b28f20c6f9e416b976bfce339baa
Reviewed-on: https://go-review.googlesource.com/c/go/+/216220
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>