CDAP-15550 Netezza db plugin enhacements: all data types support and proper test coverage

[vladhlinskiy]

JIRA: https://issues.cask.co/browse/CDAP-15550
WIKI: https://wiki.cask.co/display/CE/Netezza+database+plugin

In scope of this PR:

• Added tests for Source plugin for next types:

BYTEINT, DOUBLE PRECISION, INTEGER, NCHAR, NVARCHAR, TIMETZ

• Added tests for Sink plugin for next types:

BYTEINT, DOUBLE PRECISION, INTEGER, NCHAR, NVARCHAR, TIMETZ, BOOLEAN, CHAR, DECIMAL, FLOAT, SMALLINT, BIGINT, NUMERIC, REAL

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[vladhlinskiy]

@albertshau could you, please, take a look?

[albertshau]

lgtm