fix(Transfomers): call .toJSON in toSnakeCase

[RedGuy12]

Please describe the changes this PR makes and why it should be merged:
Makes toSnakeCase call .toJSON functions if they exist.
Fixes #8742
Status and versioning classification:

• Code changes have been tested against the Discord API, or there are no code changes

I could make calling .toJSON togglable via a boolean parameter if that is preferred to avoid breaking changes.

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[codecov]

Codecov Report

Merging #8790 (2ecca62) into main (6e348ff) will increase coverage by 0.38%.
The diff coverage is 87.62%.

❗ Current head 2ecca62 differs from pull request most recent head 70277da. Consider uploading reports for the commit 70277da to get more accurate results

@@            Coverage Diff             @@
##             main    #8790      +/-   ##
==========================================
+ Coverage   85.22%   85.61%   +0.38%     
==========================================
  Files          77       96      +19     
  Lines        6715     9459    +2744     
  Branches      877     1134     +257     
==========================================
+ Hits         5723     8098    +2375     
- Misses        953     1319     +366     
- Partials       39       42       +3     

Flag	Coverage Δ
brokers	65.24% <ø> (?)
builders	98.65% <87.87%> (-1.35%)	⬇️
collection	100.00% <ø> (ø)
proxy	81.53% <ø> (ø)
rest	91.97% <82.35%> (?)
util	100.00% <ø> (ø)
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Impacted Files	Coverage Δ
...ackages/rest/src/lib/handlers/SequentialHandler.ts	86.07% <50.00%> (ø)
packages/builders/src/components/Components.ts	87.87% <60.00%> (-12.13%)	⬇️
...ers/src/components/selectMenu/ChannelSelectMenu.ts	63.49% <63.49%> (ø)
...src/components/selectMenu/MentionableSelectMenu.ts	90.32% <90.32%> (ø)
...ilders/src/components/selectMenu/RoleSelectMenu.ts	90.32% <90.32%> (ø)
...ilders/src/components/selectMenu/UserSelectMenu.ts	90.32% <90.32%> (ø)
...ilders/src/components/selectMenu/BaseSelectMenu.ts	92.18% <92.18%> (ø)
packages/rest/src/lib/utils/utils.ts	97.33% <92.30%> (ø)
packages/builders/src/components/ActionRow.ts	100.00% <100.00%> (ø)
packages/builders/src/components/Assertions.ts	100.00% <100.00%> (ø)
... and 17 more

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[kyranet]

This makes the bold assumption that any JSON encodable will always yield snake_case properties, but that's (hopefully) almost always the case here, and for the places we use toSnakeCase for, it would be wrong to use JSON encodable classes that don't yield snake_case properties.

Either way, this seems to be triggered when using builders inside plain objects, which makes sense.

[RedGuy12]

Would it be better if I called toSnakeCase on toJSON's return value?

[suneettipirneni]

Would it be better if I called toSnakeCase on toJSON's return value?

I would personally prefer this.

Splitting functions by specific behaviors yields more flexible predictable code. toSnakeCase should only be concerned with transforming the input (as-is) to snake_case json, it shouldn't do anything else in addition to that.