Add sample payload data anonymization

[derenio]

This PR adds anonymization to the sample payloads of the GraphQL's webhookSamplePayload endpoint.

1. The changes are tested.
2. Changes are mentioned in the changelog.

[codecov]

Codecov Report

Merging #5161 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #5161   +/-   ##
=======================================
  Coverage   91.81%   91.81%           
=======================================
  Files         271      271           
  Lines       17589    17589           
  Branches     1525     1525           
=======================================
  Hits        16149    16149           
  Misses       1041     1041           
  Partials      399      399

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[django-queries]

Here is the report for ac00ec1 (mirumee/saleor @ feature/anonymize_sample_payloads)
Base comparison is 9dfd1bc.

No differences were found. (click me)

# api.benchmark checkout
  test name                                  	left count 	right count	duplicate count
  -------------------------------------------	-----------	-----------	---------------
  add billing address to checkout            	         34	         34	             20
  add shipping to checkout                   	          7	          7	              0
  checkout payment charge                    	         10	         10	              0
  complete checkout                          	          8	          8	              0
  create checkout                            	          5	          5	              1

# api.benchmark homepage
  test name                                  	left count 	right count	duplicate count
  -------------------------------------------	-----------	-----------	---------------
  retrieve main menu                         	          5	          5	              0
  retrieve product list                      	          4	          4	              0
  retrieve secondary menu                    	          5	          5	              0
  retrieve shop                              	          2	          2	              0

# api.benchmark product
  test name                                  	left count 	right count	duplicate count
  -------------------------------------------	-----------	-----------	---------------
  product details                            	         18	         18	              4
  retrieve product attributes                	          9	          9	              0

# api.benchmark variant
  test name                                  	left count 	right count	duplicate count
  -------------------------------------------	-----------	-----------	---------------
  product variant bulk create                	         51	         51	              3
  retrieve variant list                      	         23	         23	              9

# api product sorting attributes
  test name                                  	left count 	right count	duplicate count
  -------------------------------------------	-----------	-----------	---------------
  sort product not having attribute data     	         21	         21	              0