crypto/internal/fips140/bigmod: add more //go:norace annotations

crypto/internal/fips140/bigmod: add more //go:norace annotations

//go:norace does not carry over when a function is inlined.
Add //go:norace to functions that inline loops over Nat words.
Improves race tests, also asan, msan.

These are with -race:

goos: darwin
goarch: arm64
pkg: crypto/internal/fips140/bigmod
cpu: Apple M3 Pro
                  │     old      │                 new                 │
                  │    sec/op    │   sec/op     vs base                │
ModAdd-12            172.4n ± 3%   117.9n ± 3%  -31.62% (p=0.000 n=20)
ModSub-12            147.1n ± 2%   111.4n ± 3%  -24.27% (p=0.000 n=20)
NewModulus-12       12.966µ ± 1%   9.743µ ± 2%  -24.86% (p=0.000 n=20)
MontgomeryRepr-12   1305.5n ± 1%   986.3n ± 0%  -24.45% (p=0.000 n=20)
MontgomeryMul-12    1304.0n ± 1%   976.8n ± 0%  -25.10% (p=0.000 n=20)
ModMul-12            2.893µ ± 1%   2.055µ ± 3%  -28.97% (p=0.000 n=20)
ExpBig-12            2.784m ± 0%   2.789m ± 0%   +0.17% (p=0.008 n=20)
Exp-12               3.468m ± 0%   2.620m ± 0%  -24.45% (p=0.000 n=20)
geomean              7.930µ        6.073µ       -23.41%

pkg: crypto/rsa
                             │      old      │                 new                  │
                             │    sec/op     │    sec/op     vs base                │
DecryptPKCS1v15/2048-12         1.795m ±  1%   1.175m ±  1%  -34.52% (p=0.000 n=20)
DecryptPKCS1v15/3072-12         3.836m ±  2%   2.647m ±  0%  -31.01% (p=0.000 n=20)
DecryptPKCS1v15/4096-12         7.316m ±  0%   5.437m ±  0%  -25.68% (p=0.000 n=20)
EncryptPKCS1v15/2048-12         45.85µ ±  1%   34.78µ ±  0%  -24.15% (p=0.000 n=20)
DecryptOAEP/2048-12             1.793m ±  2%   1.188m ±  1%  -33.76% (p=0.000 n=20)
EncryptOAEP/2048-12             55.11µ ±  1%   43.91µ ±  1%  -20.32% (p=0.000 n=20)
SignPKCS1v15/2048-12            1.797m ±  2%   1.193m ±  0%  -33.62% (p=0.000 n=20)
VerifyPKCS1v15/2048-12          45.16µ ±  1%   34.51µ ±  0%  -23.57% (p=0.000 n=20)
SignPSS/2048-12                 1.826m ±  2%   1.213m ±  0%  -33.55% (p=0.000 n=20)
VerifyPSS/2048-12               53.25µ ±  1%   42.40µ ±  1%  -20.36% (p=0.000 n=20)
GenerateKey/2048-12             323.7m ± 33%   209.0m ± 17%  -35.43% (p=0.000 n=20)
ParsePKCS8PrivateKey/2048-12   105.26µ ±  0%   94.74µ ±  0%   -9.99% (p=0.000 n=20)
geomean                         792.5µ         574.3µ        -27.53%

Change-Id: I1f1986cf2bac126d7346799b08b17d356b28d956
Reviewed-on: https://go-review.googlesource.com/c/go/+/633995
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>