refactor!: remove tieredProxyUrls support

[barjin]

The feature has seen little adoption, and the tier rotation bled into APIs that otherwise had no business knowing about it (ProxyConfiguration pulling a Request, newProxyInfo returning a tier, browser controllers tracking a tier, etc.). In v4, the main rotation unit is the Session, so proxy-level tier rotation is redundant.

The behaviour can still be emulated idiomatically with Session and SessionPool classes (see the Upgrading guide).

Closes #3597

[Copilot]

Pull request overview

This PR removes the deprecated tieredProxyUrls proxy rotation mechanism (and the related proxyTier plumbing) to simplify the proxy/session surface area in Crawlee v4, aligning rotation around Session rather than proxy tiers.

Changes:

• Removed tieredProxyUrls support from ProxyConfiguration and eliminated tier-tracking logic.
• Removed proxyTier from ProxyInfo and from the BrowserPool/BrowserCrawler plumbing.
• Updated v4 upgrading docs and removed tiered-proxy documentation from the proxy management guide.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
test/core/proxy_configuration.test.ts	Removes tiered-proxy tests and updates imports accordingly.
packages/types/src/session.ts	Drops proxyTier from ProxyInfo type.
packages/core/src/proxy_configuration.ts	Removes tieredProxyUrls API and tier-tracker implementation; simplifies option validation and URL generation.
packages/browser-pool/src/launch-context.ts	Removes proxyTier from launch context options/state.
packages/browser-pool/src/browser-pool.ts	Removes tier-aware browser selection/launch plumbing; simplifies capacity picking based on proxy URL only.
packages/browser-pool/src/abstract-classes/browser-plugin.ts	Stops passing proxyTier into launch context construction.
packages/browser-pool/src/abstract-classes/browser-controller.ts	Removes proxyTier from controller state/docs.
packages/browser-crawler/src/internals/browser-crawler.ts	Stops passing proxyTier into BrowserPool page creation.
docs/upgrading/upgrading_v4.md	Adds a migration note + example showing how to emulate tier escalation using named sessions in SessionPool.
docs/guides/proxy_management.mdx	Removes the “Tiered proxies” section from the guide.

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[metalwarrior665]

Sad to see this go but it is understandable. We didn't really have a need for this in the Store team (other than WCC maybe). When I proposed this feature, we are churning lot of Actors that could have used this but the business changed.

I think we can implement this in userland if needed and go from there.

[l2ysho]

this looks straightforward 👍