PERF: Disable unnecessary copy in dtype conversion for buffer

[snowman2]

• Fully documented, including history.rst for all changes and api/*.rst for new API

https://numpy.org/doc/stable/reference/generated/numpy.ndarray.astype.html

By default, astype always returns a newly allocated array. If this is set to false, and the dtype, order, and subok requirements are satisfied, the input array is returned instead of a copy.

Since copy is explicitly called beforehand, copy=False should be safe.

UPDATE: see #915

[codecov]

Codecov Report

Merging #905 (d5d5fe8) into master (be6e991) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #905   +/-   ##
=======================================
  Coverage   95.37%   95.37%           
=======================================
  Files          21       21           
  Lines        1729     1729           
=======================================
  Hits         1649     1649           
  Misses         80       80           

Impacted Files	Coverage Δ
pyproj/utils.py	72.58% <100.00%> (ø)

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