docs: restructure builders docs

[maggieneterval]

Fixes: #8382
Related: #6659

Description

Restructures the builders documentation:

• Separates each build environment into a standalone page.
• Separates the builder types and build environments pages into separate subsections.

User-facing improvements:

• As reported in Improve distinction between builder and build-environments #6659, it is currently difficult to distinguish between builder types and build environments.
• Surface each build environment as a separate page when using site search or Google search.

Analytics improvements:

• Provide independent pageview metrics for each builder type and build environment page.

[codecov]

Codecov Report

Merging #8426 (26489fe) into main (290280e) will decrease coverage by 5.29%.
The diff coverage is 54.77%.

@@            Coverage Diff             @@
##             main    #8426      +/-   ##
==========================================
- Coverage   70.48%   65.19%   -5.29%     
==========================================
  Files         515      607      +92     
  Lines       23150    30100    +6950     
==========================================
+ Hits        16317    19624    +3307     
- Misses       5776     9000    +3224     
- Partials     1057     1476     +419     

Impacted Files	Coverage Δ
cmd/skaffold/app/cmd/completion.go	13.04% <0.00%> (-1.25%)	⬇️
cmd/skaffold/app/cmd/config/list.go	65.21% <ø> (ø)
cmd/skaffold/app/cmd/config/set.go	88.72% <ø> (ø)
cmd/skaffold/app/cmd/config/util.go	54.28% <ø> (ø)
cmd/skaffold/app/cmd/credits.go	100.00% <ø> (ø)
cmd/skaffold/app/cmd/credits/export.go	0.00% <0.00%> (ø)
cmd/skaffold/app/cmd/deploy.go	40.90% <0.00%> (-12.94%)	⬇️
cmd/skaffold/app/cmd/flags.go	93.00% <ø> (+2.18%)	⬆️
cmd/skaffold/app/cmd/generate_pipeline.go	60.00% <ø> (ø)
cmd/skaffold/app/cmd/inspect_modules.go	65.00% <ø> (ø)
... and 419 more

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