[FLINK-17786][sql-client] Remove dialect from ExecutionEntry

[lirui-apache]

What is the purpose of the change

Since SQL dialect is already a table config option, we don't need to support it in ExecutionEntry.

Brief change log

• Remove the dialect config from ExecutionEntry.
• Refactor test to cover switching dialect in a session.

Verifying this change

Updated test case

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn/Mesos, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? NA

[lirui-apache]

@JingsongLi Please take a look. Thanks.

[flinkbot]

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Automated Checks

Last check on commit 35ccaf9 (Fri Oct 16 10:49:47 UTC 2020)

Warnings:

• No documentation files were touched! Remember to keep the Flink docs up to date!

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Review Progress

• ❓ 1. The [description] looks good.
• ❓ 2. There is [consensus] that the contribution should go into to Flink.
• ❓ 3. Needs [attention] from.
• ❓ 4. The change fits into the overall [architecture].
• ❓ 5. Overall code [quality] is good.

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[flinkbot]

CI report:

• 35ccaf9 Azure: FAILURE

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[lirui-apache]

My personal pipeline has passed: https://dev.azure.com/lirui-apache/flink/_build/results?buildId=78&view=results

[JingsongLi]

Thanks @lirui-apache for contribution, looks good to me.