feat(core/services-gcs): support user defined metadata

[jorgehermo9]

Relates to #4842

Please do not merge yet, I'm not sure this works.

I didn't see the CI for GCS behaviour tests. Im not sure that this PR is ok, as I do not have a GCP account and couldn't find out how to test it locally. Tried it with https://github.com/fsouza/fake-gcs-server and I also couldn't figure it out. Also, I can't get the gcs behavior tests running in local

Is the behaviour test plan ok? https://github.com/apache/opendal/actions/runs/11652657364/job/32444123433#step:3:39

It seems that the gcs service is being filtered out in this condition

opendal/.github/scripts/test_behavior/plan.py

Line 59 in 330bd74

if not os.getenv("GITHUB_HAS_SECRETS") == "true":

Maybe a maintainer has to manually run that check?

[Xuanwo]

I didn't see the CI for GCS behaviour tests.

Thank you, @jorgehermo9, for working on this.

We do have tests for GCS, but GitHub has security reasons for not allowing PRs from forks to use them. (This can be addressed once you become an OpenDAL committer!)

I will try to trigger the test for you.

[Xuanwo]

Thank you @jorgehermo9, most changes LGTM, I will trigger a CI for it.

[Xuanwo]

See #5284

[Xuanwo]

Nice work!

[jorgehermo9]

Hi @Xuanwo so nice! Thank you very much.

I'm open for any other suggestions!

[Xuanwo]

Perfect. Thank you @jorgehermo9 for this great PR!