*: replace storage.Create by storage.New, upgrade dumpling CI to go 1.16

[lichunzhu]

What problem does this PR solve?

https://github.com/pingcap/br/issues/898

1. storage.Create has been deprecated... so let's replace the remaining two calls from Dumpling.
2. Dumpling originally used storage.Create(sendCreds=true), but
   the entire cloud access happens within Lightning, so we don't need to send credentials to anyone
   this introduced skipCheckPath=false.

What is changed and how it works?

1. Changed storage.Create to storage.New with sendCreds=false and skipCheckPath=true.
2. Upgrade dumpling go version to 1.16.

Check List

Tests

• Unit test
• Integration test

Side effects

Related changes

Release note

• When using Dumpling to export to S3, we no longer require s3:ListBucket permission on the entire bucket, only the data source prefix itself.

[glorv]

/lgtm

[ti-chi-bot]

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[lichunzhu]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 7165478

[lichunzhu]

/hold

[lichunzhu]

/unhold

[lichunzhu]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: b5c6bc4

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #287.

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #288.