[llvm:optimizations] [missed-optimization] Unable to hoist out call to readonly function in a loop

In clang 21.1.0 (and earlier), in the following code, which is about as reduced as I can get:

```cpp
#include

// [[gnu::noinline]]
// [[gnu::const]]
// [[gnu::noinline, gnu::const]]
static std::size_t count_ints(const int *ints) {
std::size_t num{};
while (*ints) {
num++;
ints++;
}
return num;
}

std::size_t num_compares{};

// Returns if a zero-termed list of ints has 1234
bool has_1234(const int *ints) {
for (std::size_t index = 0; index < count_ints(ints); ++index) {
++num_compares;
if (ints[index] == 1234) {
return true;
}
}
return false;
}
```
CE link: https://godbolt.org/z/raPrvq9aT

Here I would expect:
- the `count_ints` function to be noted as `const` (or similar) Certainly "pure". TBAA should note that it only reads through an `int*` if at all. Maybe `argmemonly` (I think?)
- as a result the `count_ints` is called inside the loop (even though it's cleverly been turned into a `wcslen`. I'd hope LICM could yank it out
- that results in poor performance (O(n2)) though naturally this code is awful (on purpose!)

Interestingly, marking it `gnu::const` (not strictly true) still causes the wcslen to be inlined and called every iteration. Making it `noinline` _and_ `const` "fixes" this but I think is not strictly true (as I understand it the read through `*ints` makes it non-const which is to say "readnone" in llvm).

Similar reported to [gcc](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122240).

I discussed this over Discord with a few folks more familiar with LLVM and they said to file this with the tags in the title. Sorry if this is not the correct way to do this.