Add Indices of X in List

[Burbulinis]

Description

This PR aims to add an expression to get the indices or positions of a list where the value at that index is the provided value.
The indices option is only allowed for variable lists, which returns strings. Whereas for positions it returns an integer. You can get the position of any list. For example:

set {_list::a} to 1
set {_list::b} to 2
set {_list::c} to 1
set {_list::d} to 2
set {_list::e} to 1

send all indices of the value 2 in {_list::*} # returns "b" and "c"
send all positions of the value 1 in {_list::*} # returns 1, 3, 5

send positions of value {_whatever} in (some expression that returns multiple values)
# allows non-literals and non-variable lists

This expression was merged with the current ExprIndexOf, which I renamed for clarity. The default, if you do not specify last or all is the first index/position. This is done to be consistent with the old ExprIndexOf.

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Target Minecraft Versions: any
Requirements: none
Related Issues: #3933

[Efnilite]

very nois

[sovdeeth]

I have forgotten that ExprIndexOf already exists. This needs to be merged with that

[TheAbsolutionism]

My very important review

[sovdeeth]

code looks good