installer: use temporary download

[glensc]

improves installer:

1. download to a temporary file to prevent partially downloaded executable
2. use sudo only for move package

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@3be78fe). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #784   +/-   ##
=========================================
  Coverage          ?   32.39%           
=========================================
  Files             ?       63           
  Lines             ?     4951           
  Branches          ?        0           
=========================================
  Hits              ?     1604           
  Misses            ?     3215           
  Partials          ?      132

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