in general, the value_type of a `const_iterator` is `T` instead of
`const T`, what has the const specifier is `reference`. because,
when dereferencing an iterator, the value type does not matter any
more, as it always a copy.
and GCC-14 points this out:
```
/home/kefu/dev/scylladb/sstables/compress.hh:224:13: error: type qualifiers ignored on function return type [-Werror=ignored-qualifiers]
224 | value_type operator*() const {
| ^~~~~~~~~~
/home/kefu/dev/scylladb/sstables/compress.hh:228:13: error: type qualifiers ignored on function return type [-Werror=ignored-qualifiers]
228 | value_type operator[](ssize_t i) const {
| ^~~~~~~~~~
```
so, in this change, let's change the value_type to `uint64_t`.
please note, it's not typical to return `value_type` from `operator*`
or `operator[]` of an iterator. but due to the design of
segmented_offsets, we cannot return a reference, so let's keep it
this way.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closesscylladb/scylladb#19186
9318d21a22