Spree tidy-up

[Matt-Yorkley]

What? Why?

Cleans up a few bits of old mess noticed whilst doing code review on #7947. Removes various unnecessary uses of class_eval, which modifies classes after they're loaded. Avoiding it will probably be a good idea when we're using Zeitwerk 👍

What should we test?

Green build should be enough here.

Release notes

Changelog Category: Technical changes

[codecov]

Codecov Report

Merging #7977 (6c64bce) into master (c6743d8) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 6c64bce differs from pull request most recent head 38aac70. Consider uploading reports for the commit 38aac70 to get more accurate results

@@            Coverage Diff             @@
##           master    #7977      +/-   ##
==========================================
- Coverage   93.27%   93.27%   -0.01%     
==========================================
  Files         640      639       -1     
  Lines       18152    18145       -7     
==========================================
- Hits        16931    16924       -7     
  Misses       1221     1221              

Impacted Files	Coverage Δ
app/models/calculator/price_sack.rb	100.00% <ø> (ø)
lib/spree/core.rb	96.55% <ø> (-0.12%)	⬇️
app/controllers/api/v0/base_controller.rb	100.00% <100.00%> (ø)
app/models/concerns/calculated_adjustments.rb	100.00% <100.00%> (ø)
app/models/concerns/payment_method_distributors.rb	100.00% <100.00%> (ø)
app/models/enterprise_fee.rb	100.00% <100.00%> (ø)
app/models/spree/gateway.rb	94.11% <100.00%> (+0.17%)	⬆️
app/models/spree/payment_method.rb	92.72% <100.00%> (-0.38%)	⬇️
app/models/spree/shipping_method.rb	96.61% <100.00%> (ø)
app/models/spree/tax_rate.rb	100.00% <100.00%> (ø)
... and 1 more

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[Matt-Yorkley]

Avoiding it will probably be a good idea when we're using Zeitwerk

Turns out the Zeitwerk PR fails on deployment with errors caused by... exactly the bits of code I've already tidied up here.

#PremonitionDrivenDevelopment