Enable writeback_cache and async_dio FUSE options (#7980)

* Enable writeback_cache and async_dio FUSE options

Fixes #7978

- Update mount_std.go to use EnableWriteback and EnableAsyncDio from go-fuse
- Add go.mod replace directive to use local go-fuse with capability support
- Remove temporary workaround that disabled these options

This enables proper FUSE kernel capability negotiation for writeback cache
and async direct I/O, improving performance for small writes and concurrent
direct I/O operations.

* Address PR review comments

- Remove redundant nil checks for writebackCache and asyncDio flags
- Update go.mod replace directive to use seaweedfs/go-fuse fork instead of local path

* Add TODO comment for go.mod replace directive

The replace directive must use a local path until seaweedfs/go-fuse#1 is merged.
After merge, this should be updated to use the proper version.

* Use seaweedfs/go-fuse v2.9.0 instead of local repository

Replace local path with seaweedfs/go-fuse v2.9.0 fork which includes
the writeback_cache and async_dio capability support.

* Use github.com/seaweedfs/go-fuse/v2 directly without replace directive

- Updated all imports to use github.com/seaweedfs/go-fuse/v2
- Removed replace directive from go.mod
- Using seaweedfs/go-fuse v2.0.0-20260106181308-87f90219ce09 which includes:
  * writeback_cache and async_dio support
  * Corrected module path

* Update to seaweedfs/go-fuse v2.9.1

Use v2.9.1 tag which includes the corrected module path
(github.com/seaweedfs/go-fuse/v2) along with writeback_cache
and async_dio support.

go.mod

@@ -135,7 +135,6 @@ require (
 	github.com/gin-gonic/gin v1.11.0
 	github.com/golang-jwt/jwt/v5 v5.3.0
 	github.com/google/flatbuffers/go v0.0.0-20230108230133-3b8644d32c50
-	github.com/hanwen/go-fuse/v2 v2.9.0
 	github.com/hashicorp/raft v1.7.3
 	github.com/hashicorp/raft-boltdb/v2 v2.3.1
 	github.com/hashicorp/vault/api v1.22.0
@@ -152,6 +151,7 @@ require (
 	github.com/rdleal/intervalst v1.5.0
 	github.com/redis/go-redis/v9 v9.17.2
 	github.com/schollz/progressbar/v3 v3.19.0
+	github.com/seaweedfs/go-fuse/v2 v2.9.1
 	github.com/shirou/gopsutil/v4 v4.25.11
 	github.com/tarantool/go-tarantool/v2 v2.4.1
 	github.com/tikv/client-go/v2 v2.0.7