length() over .len

[Doubleumc]

About the pull request

Replaces list.len lookup with length(list).

The following replacements are broadly applied:

• list.len -> length(list) : except where len is being assigned or modified, such as list.len--`, which is a valid use-case
• list && list.len, !isnull(list) && list.len, list?.len -> LAZYLEN(list) : also the inverted form; LAZYLEN is just a define for length but is used here to more clearly communicate that originally the list was tested for existence
• if(list.len) list.Cut() -> LAZYCLEARLIST(list) : identical to the define so instead of replacing len with length just used the define

A few one-offs:

• (list?(list.len):(0)) -> (LAZYLEN(list) || 0) in recipe.dm : resulting value gets assigned to a variable that is used elsewhere, so ensured it returned 0 in the same circumstances
• if(!list || !list.len) { return FALSE } if(list?.len) { ...-> if(!LAZYLEN(list)) { return FALSE } ... in modify_variables.dm : simplified two branching checks into one
• !list || list.len == 0 -> !LAZYLEN(list) in teleporter.dm : removed the == test to allow simplifying down to LAZYLEN while ensuring it has the same truthiness

Explain why it's good for the game

length(list) is preferred over list.len since it inherently handles nulls and is allegedly slightly more performant.

Testing Photographs and Procedure

Boots without issue.

Changelog

No player-facing changes.