feat: replace go-rpmutils library with our own (#7953)

- While doing cross-compiling of Forgejo (with CGO enabled) it was noticed that besides compiling sqlite3, github.com/DataDog/zstd (a CGO wrapper around the reference zstd library) took a long time to compile. Upon investigating why this library was included in the first place I concluded that this library is not even used and compiling this package is a waste of time and CPU cycles.
- https://github.com/sassoftware/go-rpmutils is the library that uses the CGO zstd library, and would use it the pure Go variant (https://github.com/klauspost/compress/zstd) if CGO is enabled (which is the default). It uses zstd to uncompress the payload of a RPM packages. This is a operation that Forgejo does not use in the slightest, hence being unused code.
- It is not possible to force compiling the pure Go variant if CGO is enabled. Therefore forking and removing this code is the only option to avoid compiling the zstd C library. The changes made to the fork can be seen here: https://code.forgejo.org/forgejo/go-rpmutils/compare/2660c86d578cd2a5366fe5bda488e37f9ab1b11a...v1.0.0
- Via [actiongraph](https://github.com/icio/actiongraph) you can precisely see where the Go compiler is spending time, on a beefy machine the compilation takes of the zstd C library takes ~40s. For reference compiling the sqlite3 C library takes ~50s.
- The forgejo binary (build via `make backend`) reduced its size by 835776 bytes (0.8 MiB).

TL;DR forked library to remove unused code to avoid Go spending a considerable amount of time compiling the reference zstd library that in the end is never used.

<!--start release-notes-assistant-->

## Release notes
<!--URL:https://codeberg.org/forgejo/forgejo-->
- Features
  - [PR](https://codeberg.org/forgejo/forgejo/pulls/7953): <!--number 7953 --><!--line 0 --><!--description cmVwbGFjZSBnby1ycG11dGlscyBsaWJyYXJ5IHdpdGggb3VyIG93bg==-->replace go-rpmutils library with our own<!--description-->
<!--end release-notes-assistant-->

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/7953
Reviewed-by: Earl Warren <earl-warren@noreply.codeberg.org>
Co-authored-by: Gusted <postmaster@gusted.xyz>
Co-committed-by: Gusted <postmaster@gusted.xyz>

go.mod

@@ -7,6 +7,7 @@ toolchain go1.24.3
 require (
 	code.forgejo.org/f3/gof3/v3 v3.10.6
 	code.forgejo.org/forgejo-contrib/go-libravatar v0.0.0-20191008002943-06d1c002b251
+	code.forgejo.org/forgejo/go-rpmutils v1.0.0
 	code.forgejo.org/forgejo/levelqueue v1.0.0
 	code.forgejo.org/forgejo/reply v1.0.2
 	code.forgejo.org/go-chi/binding v1.0.1
@@ -87,7 +88,6 @@ require (
 	github.com/redis/go-redis/v9 v9.8.0
 	github.com/robfig/cron/v3 v3.0.1
 	github.com/santhosh-tekuri/jsonschema/v6 v6.0.1
-	github.com/sassoftware/go-rpmutils v0.4.0
 	github.com/sergi/go-diff v1.3.2-0.20230802210424-5b0b94c5c0d3
 	github.com/shurcooL/vfsgen v0.0.0-20230704071429-0000e147ea92
 	github.com/stretchr/testify v1.10.0
@@ -121,7 +121,6 @@ require (
 	dario.cat/mergo v1.0.0 // indirect
 	filippo.io/edwards25519 v1.1.0 // indirect
 	git.sr.ht/~mariusor/go-xsd-duration v0.0.0-20220703122237-02e73435a078 // indirect
-	github.com/DataDog/zstd v1.5.5 // indirect
 	github.com/Microsoft/go-winio v0.6.2 // indirect
 	github.com/RoaringBitmap/roaring/v2 v2.4.5 // indirect
 	github.com/andybalholm/brotli v1.1.1 // indirect
@@ -152,7 +151,7 @@ require (
 	github.com/caddyserver/zerossl v0.1.3 // indirect
 	github.com/cention-sany/utf7 v0.0.0-20170124080048-26cad61bd60a // indirect
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
-	github.com/cloudflare/circl v1.6.0 // indirect
+	github.com/cloudflare/circl v1.6.1 // indirect
 	github.com/cpuguy83/go-md2man/v2 v2.0.5 // indirect
 	github.com/cyphar/filepath-securejoin v0.3.6 // indirect
 	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc // indirect