Switch to modern flow syntax for utility types and bounds

[SamChou19815]

Depends on #469

[github-actions]

workflow: benchmarks/size

Comparison of minified (terser) and compressed (brotli) size results, measured in bytes. Smaller is better.

Results	Base	Patch	Ratio
react-strict-dom/dist/web/index.js
· compressed	3,251	3,251	1.00
· minified	10,375	10,375	1.00
react-strict-dom/dist/web/runtime.js
· compressed	1,645	1,645	1.00
· minified	4,131	4,131	1.00
react-strict-dom/dist/native/index.js
· compressed	16,580	16,580	1.00
· minified	64,168	64,168	1.00
react-strict-animated/dist/web/index.js
· compressed	6,861	6,861	1.00
· minified	23,486	23,486	1.00
react-strict-animated/dist/native/index.js
· compressed	797	797	1.00
· minified	2,518	2,518	1.00

[github-actions]

workflow: benchmarks/perf (native)

Comparison of performance test results, measured in operations per second. Larger is better.

Results	Base	Patch	Ratio
css.create
· small	1,154,142	1,124,278	0.97	-
· small with units	505,298	492,270	0.97	-
· small with variables	666,499	658,813	0.99	-
· several small	357,706	346,623	0.97	-
· large	201,637	200,151	0.99	-
· large with polyfills	147,712	148,324	1.00	+
· complex	100,921	101,988	1.01	+
· unsupported	211,256	209,568	0.99	-
css.createTheme
· simple theme	220,560	220,651	1.00	+
· polyfill theme	209,243	209,171	1.00	-