[BEAM-3348] Set utf-16 as SQL DSL default charset

[Alienero]

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[Alienero]

R: @xumingmin

[mingmxu]

retest this please

[Alienero]

hi @xumingmin , I hava run mvn clean verify in beam/sdks/java/extensions/sql, all unit test passed. please take a look

[Alienero]

retest this please.

[robertwb]

What's the motivation for UTF-16? Everywhere else we seem to use UTF-8.

[mingmxu]

Given that Calcite only support UTF16 and ISO-8859-1(LATIN1)[1], this sounds a good option in SQL component, and it's also the solution in other projects like Flink[2].

@Alienero there're another two properties in SaffronProperties.java, is it safe to ignore them?

[1]. http://mail-archives.apache.org/mod_mbox/calcite-dev/201710.mbox/%3CCAPSgeETv5aJ3GKAkoYhCN7oihu9cNLwwLFrs7AsTmC-9WTk2aw@mail.gmail.com%3E
[2]. https://issues.apache.org/jira/browse/FLINK-7451

[Alienero]

hi @xumingmin，I made some additions: add default national charset and collation. uft-16 also as default charset for the N'string' construct

R: @xumingmin

[mingmxu]

retest this please

[mingmxu]

LGTM, merging

[mingmxu]

retest this please