Kingston/Sutton Echo changes

[dracos]

For https://github.com/mysociety/societyworks/issues/4725 (core ID changes) [skip changelog]

This PR starts with some core changes - simplifying a bit of code to auto-use it where needed (will be useful in future), finds some more Echo IDs that were previously missed, changing the garden end date format, and making sure shared Kingston/Sutton code uses no fixed IDs at all (as they will change over independently of each other at different times).

It then makes a copy of the SLWP code, removes now-unneeded parts of that, and updates with new Echo IDs and locations for data (but at that point is not used by anything). After that's done, it moves Sutton and then Kingston to the new SLWP copy, also removing unneeded parts of the code and updating for new Echo IDs and locations.

Bulky and Garden tests are marked to be skipped; the coverage stats are poor because at this point we're not dealing correctly with requests, garden, or bulky, and much of the copied code is not yet being tested.

For going live, as Sutton is going live before Kingston, the Sutton commits can be taken out and merged separately without the Kingston ones; both can go on staging at present for testing.

[codecov]

Codecov Report

Attention: Patch coverage is 90.29650% with 36 lines in your changes missing coverage. Please review.

Project coverage is 82.26%. Comparing base (98764b8) to head (36822b4).

Files with missing lines	Patch %	Lines
perllib/FixMyStreet/Roles/Cobrand/SLWP2.pm	90.75%	12 Missing and 15 partials ⚠️
perllib/FixMyStreet/Cobrand/Sutton.pm	82.05%	6 Missing and 1 partial ⚠️
perllib/FixMyStreet/Cobrand/Kingston.pm	92.85%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5334      +/-   ##
==========================================
- Coverage   82.43%   82.26%   -0.17%     
==========================================
  Files         416      417       +1     
  Lines       32979    33283     +304     
  Branches     5308     5367      +59     
==========================================
+ Hits        27186    27381     +195     
- Misses       4220     4304      +84     
- Partials     1573     1598      +25     

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