feat(services/goosefs): bump goosefs-sdk to 0.2.1 and expose cache features

[XuQianJin-Stars]

Which issue does this PR close?

Closes #.

Rationale for this change

goosefs-sdk 0.2.1 compiles the client metadata cache and the disk-backed page
cache only behind Cargo features, so the default client stays a gRPC data plane.
OpenDAL currently depends on 0.1.9, which does not expose those features and
cannot compile the 0.2.1 cache backends.

Forwarding the opt-in features lets applications enable the caches without
pulling lru, foyer, or io_uring into every services-goosefs build.

What changes are included in this PR?

• Bump goosefs-sdk from 0.1.9 to 0.2.1 with default-features = false.

• Add opt-in features on opendal-service-goosefs and the opendal facade:

  Facade feature	Service crate feature
  services-goosefs-metadata-cache	metadata-cache
  services-goosefs-page-cache	page-cache
  services-goosefs-page-cache-io-uring	page-cache-io-uring

• Document how to enable the features and the runtime knobs
  (GOOSEFS_METADATA_CACHE_ENABLED, GOOSEFS_USER_CLIENT_CACHE_ENABLED).

• Drop the 0.1.9 note that $GOOSEFS_CONF_DIR was ignored; 0.2.1 reads it.

Are there any user-facing changes?

Yes.

• services-goosefs now tracks goosefs-sdk 0.2.1. The default GooseFS build
  no longer enables the SDK's old metrics-pushgateway default.
• Cache support is opt-in. Compiling a cache feature does not replace runtime
  configuration: metadata cache is on by default once compiled; page cache
  stays off until GOOSEFS_USER_CLIENT_CACHE_ENABLED=true (and cache dirs)
  are set.
• page-cache-io-uring already enables page-cache. io_uring is Linux-only;
  other targets still build the portable tokio::fs store.

Example:

cargo add opendal --features services-goosefs,services-goosefs-metadata-cache,services-goosefs-page-cache-io-uring

[XuQianJin-Stars]

CI Error Link：#8271

[Xuanwo]

This should not be exposed at opendal side.

[Xuanwo]

Nice change, thank you!