Augment LINST instrument read buffer

[regisoc]

Brief summary of changes

For LINST instruments, some can have very long line (i.e. lots of options for select/dropdown).
These lines are bigger than the currently defined buffer read size i.e. 4K and triggers visible warnings.

E.g. for HBCD, one instrument generated from REDCap has one line with 15869 characters.
The line is truncated and some select options cannot be read.

https://github.com/aces/HBCD/issues/1725

This PR pushes the buffer size to 128K.

Testing instructions (if applicable)

1. Try accessing a LINST instrument with a very long line.

E.g.

# replace `...` with more values 
select{@}very_long_line{@}This line is very long{@}NULL=>''{-}'1'=>'0.1'{-}'2'=>'0.2'{-}'3'=>'0.3'{-}'4'=>'0.4'{-}'5'=>'0.5'{-}'6'=>'0.6'{-}'7'=>'0.7'{-}'8'=>'0.8'{-}'9'=>'0.9'{-}'10'=>'1.0'{-}'11'=>'1.1'{-}'12'=>'1.2'{-}'13'=>'1.3'{-}'14'=>'1.4'{-}'15'=>'1.5'{-}'16'=>'1.6'{-}'17'=>'1.7'{-}'18'=>'1.8'{-}'19'=>'1.9'{-}....