Include base/ platform from VS Code, adopt DomScrollableElement and introduce esbuild

[Tyriar]

Succeeds #5076

[Tyriar]

I stopped this briefly to work on some debt and to bring some of the changes here into main in smaller PRs. Doing some tables to better understand where we want to go:

Here is the current main output usage:

Use	Path	Format	Runtime	Note
Demo (/ and /test)	demo/dist/client-bundle.js	bundle	browser	Used in API/playwright tests
	out/	tsc	-	Used for core and addons
Unit tests	out/	tsc	node.js	Running in a real browser would be nice
API tests	out-test/api/	tsc	node.js	Removed in #5080
Integration tests	out-test/playwright/	tsc	node.js
Benchmark	out-test/benchmark/	tsc	node.js
@xterm/xterm package	lib/xterm.js	bundle	browser
@xterm/headless package	headless/lib-headless/xterm-headless.js	bundle	node.js

And the current output usage on this branch (I think):

Use	Path	Format	Runtime	Note
Demo (/ and /test)	demo/dist/client-bundle.js	bundle	browser	Used in API/playwright tests
	out-tsc/	tsc	-	Used for image addon only
	out-esbuild/	esbuild	-	Used for ligatures addon only
	lib/	esbuild	-	Used for core and other addons (this might require packaging atm?)
Unit tests	out-tsc/	tsc	node.js	Running in a real browser would be nice
API tests	out-tsc/test-api/	tsc	node.js
Integration tests	out-tsc/test-playwright/	tsc	node.js
Benchmark	out-tsc/test-benchmark/	tsc	node.js
@xterm/xterm package	lib/xterm.js	bundle	browser
@xterm/headless package	headless/lib-headless/xterm-headless.js	bundle	node.js

[Tyriar]

main:

Proposal (probably needs a different PR):

[jerch]

@Tyriar Plz just ping me, if you think this is ready to have a look from my side. Seems there are still some merge conflicts from your ESM transition, and I dont want to interfere in the middle of that transition to not over-complicate things.

[Tyriar]

@jerch yep planning on closing and redoing this PR today, the next one will be significantly smaller (ignoring base/) since esbuild was added in the other PR

[Tyriar]

Closing in favor of #5096