CLEANUP: log: Return `size_t` from `sess_build_logline_orig()`

CLEANUP: log: Return `size_t` from `sess_build_logline_orig()`

`sess_build_logline_orig()` takes a `size_t maxsize` as input and accordingly
should also return `size_t` instead of `int` as the resulting length. In
practice most of the callers already stored the result in a `size_t` anyways.
The few places that used an `int` were adjusted.

This Coccinelle patch was used to check for completeness:

    @@
    type T != size_t;
    T var;
    @@

    (
    * var = build_logline(...)
    |
    * var = build_logline_orig(...)
    |
    * var = sess_build_logline(...)
    |
    * var = sess_build_logline_orig(...)
    )

Reviewed-by: Volker Dusch <github@wallbash.com>