feat(std): Stabilize 'os_str_bytes' feature

Closes rust-lang#111544

…iaskrgr

Rollup of 7 pull requests

Successful merges:

 - rust-lang#114349 (rustc_llvm: Link to `zlib` on dragonfly and solaris)
 - rust-lang#114845 (Add alignment to the NPO guarantee)
 - rust-lang#115427 (kmc-solid: Fix `is_interrupted`)
 - rust-lang#115443 (feat(std): Stabilize 'os_str_bytes' feature)
 - rust-lang#115444 (Create a SMIR visitor)
 - rust-lang#115449 (Const-stabilize `is_ascii`)
 - rust-lang#115456 (Add spastorino on vacation)

r? `@ghost`
`@rustbot` modify labels: rollup

Background:

When I was migrating `PathBuf` to `Utf8PathBuf`, etc, I found out some regression in our benchmarks. Then I found out `as_str` is actually not cost-free as in the older version of rustc there's no way to get the underlying bytes out of an `OsStr` until 1.74.0.

In this PR, with the help of [`OsStr::as_encoded_bytes`](rust-lang/rust#115443) was stabilized in 1.74.0, We can perform a cost-free conversion from `&OsStr` to `&str` with constraint of it's underlying bytes are `UTF-8` encoded.

Benchmark:

With the benchmark included in the PR, the time cost is a constant now.

Result:
```
// String length of 10
osstr to_str/10 
                        time:   [5.9769 ns 5.9913 ns 6.0060 ns]
osstr as_encoded_bytes/10 
                        time:   [554.90 ps 558.32 ps 562.19 ps]

// String length of 100
osstr to_str/100
                        time:   [6.6113 ns 6.6250 ns 6.6404 ns]
osstr as_encoded_bytes/100
                        time:   [553.18 ps 557.33 ps 561.68 ps]

// String length of 1000
osstr to_str/1000
                        time:   [26.990 ns 27.033 ns 27.086 ns]
osstr as_encoded_bytes/1000
                        time:   [553.66 ps 560.67 ps 570.42 ps]

// String length of 10000
osstr to_str/10000
                        time:   [310.17 ns 310.77 ns 311.32 ns]
osstr as_encoded_bytes/10000
                        time:   [550.98 ps 555.16 ps 559.53 ps]
```