feat(cli): add prismaSchemaFolder support to prisma generate via mergeSchemas

[jkomyno]

This PR closes https://github.com/prisma/team-orm/issues/1043.
It likely works out of the box to Prisma Studio due to backward compatibility (to check later, once migrate is done), so this PR also contributes to https://github.com/prisma/team-orm/issues/1044.

[github-actions]

size-limit report 📦

Path	Size
packages/client/runtime/library.js	179.77 KB (0%)
packages/client/runtime/library.d.ts	81 B (0%)
packages/client/runtime/binary.js	600.89 KB (0%)
packages/client/runtime/binary.d.ts	26 B (0%)
packages/client/runtime/edge.js	159.02 KB (0%)
packages/client/runtime/edge-esm.js	158.91 KB (0%)
packages/client/runtime/wasm.js	114.85 KB (0%)
packages/client/runtime/index-browser.js	33.77 KB (0%)
packages/client/runtime/index-browser.d.ts	89 B (0%)
packages/cli/build/index.js	2.09 MB (+0.05% 🔺)
packages/client/prisma-client-0.0.0.tgz	3.02 MB (-0.01% 🔽)
packages/cli/prisma-0.0.0.tgz	3.74 MB (+0.01% 🔺)
packages/bundle-size/da-workers-libsql/output.tgz	888.14 KB (0%)
packages/bundle-size/da-workers-neon/output.tgz	966.74 KB (0%)
packages/bundle-size/da-workers-pg/output.tgz	985.47 KB (0%)
packages/bundle-size/da-workers-pg-worker/output.tgz	941.18 KB (0%)
packages/bundle-size/da-workers-planetscale/output.tgz	903.56 KB (0%)
packages/bundle-size/da-workers-d1/output.tgz	861.2 KB (0%)

[SevInf]

Few nitpicks and questions, other than that - looks good. Once tests are green we can merge it, i think.

[codspeed-hq]

CodSpeed Performance Report

Merging #24127 will improve performances by 31.46%

_{Comparing feat/generate-prismaSchemaFolder (8032811) with main (23aba0b)}

Summary

⚡ 1 improvements
✅ 2 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	feat/generate-prismaSchemaFolder	Change
⚡	client generation 100 models with relations	40.7 s	30.9 s	+31.46%