refactor(fgs/application): adjust function and test coding

[Lance52259]

What this PR does / why we need it:
For the function resource, adjust the function and corresponding acceptance test coding.

Which issue this PR fixes:
(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged)
fixes #xxx

Special notes for your reviewer:

Release note:

1. adjust function and test coding.

PR Checklist

• Tests added/passed.

 ./scripts/coverage.sh -o fgs -f TestAccApplication_basic
Prepare to calculate the coverage the following command:
TF_ACC=1 go test "./huaweicloud/services/acceptance/fgs" -v -coverprofile="./huaweicloud/services/acceptance/fgs/fgs_coverage.cov" -coverpkg="./huaweicloud/services/fgs" -run TestAccApplication_basic -timeout 360m -parallel 10
=== RUN   TestAccApplication_basic
=== PAUSE TestAccApplication_basic
=== CONT  TestAccApplication_basic
--- PASS: TestAccApplication_basic (87.71s)
PASS
coverage: 10.2% of statements in ./huaweicloud/services/fgs
ok      github.com/huaweicloud/terraform-provider-huaweicloud/huaweicloud/services/acceptance/fgs       87.765s coverage: 10.2% of statements in ./huaweicloud/services/fgs

• Documentation updated.

• Schema updated.

• CheckDeleted.

  • a. During query operation (Read Context)
    aa. Resource not found
    >>>>>> Paste the screenshot here <<<<<<

  • b. During delete/disassociate/unbind operation (Delete Context)
    ba. Resource not found
    >>>>>> Paste the screenshot here <<<<<<

[github-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This PR has been approved by: @Lance52259