Replace every mention of "blacklist"

Nobody has claimed this yet.

This issue has been migrated from [#15277](https://github.com/matrix-org/synapse/issues/15277).

---

### Description

The terms "black list" and "white list" are racist.

This Internet Standard draft explains it quite well:

https://www.ietf.org/archive/id/draft-knodel-terminology-13.txt

```
2.2. Blacklist-Whitelist

The metaphorical use of white-black to connote good-evil is
exclusive. While master-slave might seem like a more egregious
example of racism, white-black is arguably worse because it is more
pervasive and therefore more insidious. While recent headlines have
decried the technical community's use of master-slave, there is far
less discussion about white-black despite its importance. There is
even a name for this pervasive language pitfall: the association of
white with good and black with evil is known as the "bad is black
effect" [Grewal].
```

I propose adding block lists and allow lists and later deprecate and remove the offending terms.

### Steps to reproduce

Ask some black people for their opinion

### Homeserver

example.org

### Synapse Version

none

### Installation Method

Other (please mention below)

### Database

none

### Workers

I don't know

### Platform

-

### Configuration

_No response_

### Relevant log output

```shell
none
```

### Anything else that would be useful to know?

_No response_

No files, tests, or entry points are identified. Start by searching the repository for every occurrence of “blacklist” and “white list”, then map the affected code, configuration, and documentation before deciding the replacement scope. Done means all relevant mentions use the proposed terminology without breaking references or tests.

Written by the indexing model from the issue text.