Merge #10835: Rename member field according to the style guide

Merge #10835: Rename member field according to the style guide

4d4fb33fc Rename member field according to the style guide. (Pavel Janík)

Pull request description:

  After #10193, approx. five instances of this warning are printed when compiling with `-Wshadow`:

  ```
  In file included from txmempool.cpp:14:
  ./reverse_iterator.h:20:22: warning: declaration shadows a field of 'reverse_range<T>' [-Wshadow]
      reverse_range(T &x) : x(x) {}
                       ^
  ./reverse_iterator.h:17:8: note: previous declaration is here
      T &x;
         ^
  1 warning generated.
  ```

Tree-SHA512: 6c07c2ed6f4f232a3a8bdcdd6057040967c74552fd29d80f42e8a453b95baf203c410aa31dccc08ff2e765cbba02b1a282f6ea7804955f09b31ab20ef383792e