Consider a different bit value for `SH_WASMTIME_NOT_EXECUTED`

> Note that this has the same value as `SHF_WRITE`, so this happens to work for `.text` sections, but seems like it was only by chance. I'm not sure which bit would be better though (if we use an OS or PROC bit then probably the reader side would need an additional OS or machine check too).

_Originally posted by @philipc in [#14096](https://github.com/bytecodealliance/wasmtime/pull/14096/changes#r3742372260)_

We probably shouldn't be colliding with bits already allocated to other definitions as that may just cause confusion.

Start by locating the definitions and reader-side handling of SH_WASMTIME_NOT_EXECUTED and SHF_WRITE in the Wasmtime source. Determine which available bit avoids collisions and whether the reader requires an OS or machine check; done means the flag has a distinct value and the related read/write paths remain consistent.

Written by the indexing model from the issue text.