feat: improve generation of bundled assets (#8143)

- Replace the current vfsgen with our own bindata generator.
- zstd is used instead of gzip. This reduces the size of the resulting binary by 2MiB, the size of the bundled assets were thus reduced from 13MiB to 11MiB.
- If [the browser accepts zstd encoding](https://caniuse.com/zstd), then the compressed bytes can be served directly, otherwise it falls back to being compressed by gzip if it's not disabled via `[server].ENABLE_GZIP`
- The compression and decompression speed is roughly 4 times faster.
- The generated filesystem is now of type `fs.Fs` instead of `http.FileSystem`, this slightly simplifies the generated code and
handling of the assets.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/8143
Co-authored-by: Gusted <postmaster@gusted.xyz>
Co-committed-by: Gusted <postmaster@gusted.xyz>

go.mod

@@ -89,7 +89,6 @@ require (
 	github.com/robfig/cron/v3 v3.0.1
 	github.com/santhosh-tekuri/jsonschema/v6 v6.0.2
 	github.com/sergi/go-diff v1.4.0
-	github.com/shurcooL/vfsgen v0.0.0-20230704071429-0000e147ea92
 	github.com/stretchr/testify v1.10.0
 	github.com/syndtr/goleveldb v1.0.0
 	github.com/ulikunitz/xz v0.5.12
@@ -222,7 +221,6 @@ require (
 	github.com/rogpeppe/go-internal v1.13.1 // indirect
 	github.com/rs/xid v1.6.0 // indirect
 	github.com/russross/blackfriday/v2 v2.1.0 // indirect
-	github.com/shurcooL/httpfs v0.0.0-20230704072500-f1e31cf0ba5c // indirect
 	github.com/sirupsen/logrus v1.9.3 // indirect
 	github.com/skeema/knownhosts v1.3.0 // indirect
 	github.com/ssor/bom v0.0.0-20170718123548-6386211fdfcf // indirect
@@ -246,8 +244,6 @@ require (
 
 replace github.com/hashicorp/go-version => github.com/6543/go-version v1.3.1
 
-replace github.com/shurcooL/vfsgen => github.com/lunny/vfsgen v0.0.0-20220105142115-2c99e1ffdfa0
-
 replace github.com/nektos/act => code.forgejo.org/forgejo/act v1.26.0
 
 replace github.com/mholt/archiver/v3 => code.forgejo.org/forgejo/archiver/v3 v3.5.1