Rename wxfile asdf header

[marscher]

Changes

• Refactored/deprecated WeldxFile.show_asdf_header to header.
• Use packaging.version instead of distutils.version (deprecated).

Related Issues

Closes #688, #693

Checks

• updated CHANGELOG.rst
• updated tests
• updated doc/

[codecov]

Codecov Report

Merging #694 (882e628) into master (2c348c5) will increase coverage by 0.00%.
The diff coverage is 85.71%.

@@           Coverage Diff           @@
##           master     #694   +/-   ##
=======================================
  Coverage   96.08%   96.08%           
=======================================
  Files          92       92           
  Lines        6327     6330    +3     
=======================================
+ Hits         6079     6082    +3     
  Misses        248      248           

Impacted Files	Coverage Δ
weldx/asdf/util.py	90.20% <66.66%> (ø)
weldx/asdf/file.py	97.08% <100.00%> (+0.03%)	⬆️

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[github-actions]

Unit Test Results

       1 files  ±0         1 suites  ±0   1m 27s ⏱️ -31s
2 101 tests ±0  2 101 ✔️ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 882e628. ± Comparison against base commit 2c348c5.

♻️ This comment has been updated with latest results.