Convert nightly from a feature flag to a compiler flag

[ranile]

Description

Fixes #2754

Checklist

• I have reviewed my own code
• I have added tests updated CI to run tests

[github-actions]

Visit the preview URL for this PR (updated for commit 0b843f7):

https://yew-rs-api--pr2827-nightly-yew-compiler-pt5313ki.web.app

_{(expires Sun, 21 Aug 2022 18:00:57 GMT)}

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[github-actions]

Benchmark - SSR

Yew Master

Benchmark	Round	Min (ms)	Max (ms)	Mean (ms)	Standard Deviation
Baseline	10	453.023	473.282	461.469	7.654
Hello World	10	1291.295	1336.001	1311.833	15.482
Function Router	10	4543.684	4639.156	4574.818	26.212
Concurrent Task	10	1012.169	1014.470	1013.177	0.714

Pull Request

Benchmark	Round	Min (ms)	Max (ms)	Mean (ms)	Standard Deviation
Baseline	10	450.119	473.804	459.946	8.046
Hello World	10	1283.951	1336.869	1313.820	17.147
Function Router	10	4493.039	4567.824	4525.031	27.217
Concurrent Task	10	1011.376	1013.619	1012.286	0.746

[github-actions]

Size Comparison

examples	master (KB)	pull request (KB)	diff (KB)	diff (%)
boids	168.591	168.590	-0.001	-0.001%
contexts	106.704	106.697	-0.007	-0.006%
counter	84.323	84.323	0	0.000%
counter_functional	84.963	84.962	-0.001	-0.001%
dyn_create_destroy_apps	87.275	87.277	+0.002	+0.002%
file_upload	100.852	100.853	+0.001	+0.001%
function_memory_game	162.247	162.241	-0.006	-0.004%
function_router	343.427	343.427	0	0.000%
function_todomvc	157.192	157.195	+0.003	+0.002%
futures	221.177	221.179	+0.002	+0.001%
game_of_life	104.537	104.536	-0.001	-0.001%
immutable	180.215	180.213	-0.002	-0.001%
inner_html	81.438	81.438	-0.001	-0.001%
js_callback	110.019	110.026	+0.008	+0.007%
keyed_list	192.825	192.825	0	0.000%
mount_point	84.122	84.124	+0.002	+0.002%
nested_list	111.504	111.503	-0.001	-0.001%
node_refs	91.232	91.228	-0.005	-0.005%
password_strength	1547.433	1547.434	+0.001	+0.000%
portals	94.743	94.743	0	0.000%
router	312.878	312.876	-0.002	-0.001%
simple_ssr	150.679	150.665	-0.014	-0.009%
ssr_router	388.935	388.943	+0.009	+0.002%
suspense	107.702	107.704	+0.002	+0.002%
timer	87.096	87.096	0	0.000%
todomvc	138.570	138.570	0	0.000%
two_apps	84.983	84.983	0	0.000%
web_worker_fib	149.949	149.959	+0.010	+0.007%
webgl	85.117	85.118	+0.001	+0.001%

✅ None of the examples has changed their size significantly.

[futursolo]

Looks good to me. This should make the development process easier.

[futursolo]

Suggested change

	RUSTFLAGS: ${{ matrix.toolchain == 'nightly && '--cfg nightly_yew' || '' }}
	RUSTFLAGS: ${{ matrix.toolchain == 'nightly' && '--cfg nightly_yew' || '' }}

Oops, didn't find this during the review.