Request for Access to "Inbound Filters" for all Paid plans

### Problem Statement

Created on behalf of user, exchange can be found internally in ticket [#149338](https://sentry.zendesk.com/agent/tickets/149338)

To quote customer:

"We love Sentry, but we're small. We're on a team plan, and we're careful to avoid exceeding our quota to keep our costs manageable.

Sentry ends up ingesting a lot of events we don't care about. We used to set these to "ignore", before we found out that that ignored events count still count towards quota. Ive looked into client-side filtering, but it's a pain because we'd have to filter in 3 places (backend, frontend, mobile app).

We've just been bitten by this yet again -- a third JS party library that will go unnamed (*cough* glassbox *cough*) generated 50k events over the weekend which decimates our quota for the month. We don't have any control over this code erroring, we don't even host it, so the best we can do is turn it off, which impacts our product team.

Determined to solve this problem, I asked your documentation AI about this and it suggested Inbound Filters. My joy at discovering this feature turned to irritation when I realised it's not available on our paid plan.

It seems a tiny bit evil to be withholding a feature for managing your usage costs from all but the most expensive paid plans, don't you think? Given client side filtering is unfeasible for our tiny team, how do you suggest we handle this? And would you guys ever consider making this (in my humble opinion) critical usage management feature available to all users?

Just to put a finer point on it: as a product decision, it seems fundamentally unfair to restrict this quota management feature for users on low-tier plans; smaller customers like us are the ones who need this feature the most. We totally understand the need to paywall more enterprisey features like SAML or BAAs, but custom filtering seems very much like something that users on all plans would need. To customers like us, it leaves a bad taste in our mouth, because it gives the impression that Sentry (whether intentionally or not) wants low-tier customers to exceed their quota because it will incentivize them to move to a more expensive plan.

Regarding Spike Protection, SDK Side Filtering, Metric Alerts, Inbound Filter for browser extensions:: thanks, we've already got these enabled and they are helpful."

### Solution Brainstorm

Asking for ability to have inbound filtering enabled for all paid plans and above details their reasonings.

### Product Area

Ingestion and Filtering

Read issue #89418 and the referenced internal ticket #149338 first. The issue names no repository files, tests, or entry points; investigate the Ingestion and Filtering product area to determine the plan-eligibility change and define how completion would be verified for all paid plans.

Written by the indexing model from the issue text.