[MINOR] Increase Memory Estimate for Frames

[Baunsgaard]

This commit increases the default estimate of frame size. Previously, frames were estimated similarly to Matrices. The wrong estimate leads to problems on frames of > Integer rows. To improve it, this commit defaults to 8 character strings on all cells. In an unread matrix.

Since there is no way of knowing if the input Frame contains longer strings, it is still a subpar estimate. However,
it is an improvement overestimating everything as a dense double Matrix.

(The change happened because I encountered very incorrect estimates in BEWARE)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.06%. Comparing base (29b4d92) to head (e095cf1).
Report is 2 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2158      +/-   ##
============================================
- Coverage     72.06%   72.06%   -0.01%     
- Complexity    43964    43972       +8     
============================================
  Files          1443     1443              
  Lines        166239   166246       +7     
  Branches      32453    32455       +2     
============================================
+ Hits         119797   119798       +1     
- Misses        37182    37194      +12     
+ Partials       9260     9254       -6     

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