[v12.0/forgejo] several fixes of ALT Package registry (#8480)

**Backport:** https://codeberg.org/forgejo/forgejo/pulls/8475

closes #7946

- The `rpmsRepoPattern` regex has been fixed to handle releases with dots correctly. For example, the version `0.9.0-alt1.git.17.g2ba905d` is valid, just like `0.1.0-1.n1` mentioned in the issue (https://codeberg.org/forgejo/forgejo/issues/7946#issue-1628991)

- getEntries now returns entry names. In the integration tests, there were lines like:
```go
assert.Equal(t, []string{"", ""}, result.ProvideNames)
```
and it’s unclear how such test logic could have ever worked correctly (fixes problems with deps https://codeberg.org/forgejo/forgejo/issues/7946#issuecomment-5109795)

- ALT is an acronym for ALT Linux Team, so `Alt` was replaced with `ALT`. Strictly speaking, it should probably be `ALT Linux`, but since we use `Arch` instead of `Arch Linux`, this seems fine. Also, Distrowatch shows `Arch`/`ALT` in its dropdown, so it’s consistent.

- The strings `"Alt Linux Team"` and `"Sisyphus"` in the `Origin` and `Suite` fields have been replaced with `setting.AppName` and `"Unknown"`. `Unknown` is a valid value and is set by default, so this won’t cause any issues.

- The documentation link has been fixed: (404 docs.gitea.com/usage/packages/alt/ -> 200 forgejo.org/docs/latest/user/packages/alt/)

Co-authored-by: Maxim Slipenko <maks1ms@altlinux.org>
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/8480
Reviewed-by: Earl Warren <earl-warren@noreply.codeberg.org>
Co-authored-by: forgejo-backport-action <forgejo-backport-action@noreply.codeberg.org>
Co-committed-by: forgejo-backport-action <forgejo-backport-action@noreply.codeberg.org>

models/packages/package.go

@@ -125,7 +125,7 @@ func (pt Type) Name() string {
 	case TypeRpm:
 		return "RPM"
 	case TypeAlt:
-		return "Alt"
+		return "ALT"
 	case TypeRubyGems:
 		return "RubyGems"
 	case TypeSwift: