chore: update Cargo lint spelling and PR stack guidance

[wan9chi]

Motivation

Cargo warns that the hyphenated unit-bindings lint key is deprecated. Use unit_bindings to preserve the existing warning level without the deprecation warning.

Clarify that gh stack applies when creating a stack of pull requests.

[github-actions]

fspy benchmark

linux

dynamic/launch             change  +0.56%  [ -7.63% .. +10.07%]  overhead  +262.11%
dynamic/access             change  +0.31%  [ -1.24% ..  +1.55%]  overhead   +14.06%
dynamic/access-relative    change  +0.11%  [ -0.90% ..  +1.01%]  overhead   +61.12%
dynamic/access-contended   change  -0.27%  [ -2.45% ..  +1.72%]  overhead   +14.96%
static/launch              change  +0.92%  [ -5.44% ..  +5.72%]  overhead  +732.08%
static/access              change  -0.32%  [ -1.51% ..  +0.59%]  overhead  +809.42%
static/access-relative     change  -0.03%  [ -1.03% ..  +1.19%]  overhead +1391.18%
static/access-contended    change  +0.14%  [ -0.85% ..  +0.72%]  overhead +3214.15%

macos

dynamic/launch             change  -0.39%  [ -5.20% ..  +6.04%]  overhead  +224.25%
dynamic/access             change  +1.75%  [ -5.37% .. +39.04%]  overhead    +4.97%
dynamic/access-relative    change  -1.33%  [-11.44% ..  +6.49%]  overhead  +261.43%
dynamic/access-contended   change  +0.77%  [ -4.11% .. +13.40%]  overhead    +4.76%

windows

dynamic/launch             change  -0.48%  [ -8.63% ..  +7.09%]  overhead   +24.40%
dynamic/access             change  -0.19%  [ -1.10% ..  +0.74%]  overhead    +0.94%
dynamic/access-relative    change  +0.00%  [ -0.90% ..  +1.26%]  overhead    +1.12%
dynamic/access-contended   change  -0.17%  [-14.22% ..  +2.80%]  overhead    +1.24%