Added support to read SQL Warnings after ResultSet is read completely

[cheenamalhotra]

As of now JDBC driver does not capture any warnings after ResultSet is fully consumed and the TDS_MSG tokens are not consumed but are left unused in Stream.

Use Case:
Capturing warnings at the end of ResultSet is helpful for PolyBase External Data tables where rows could get rejected due to bad column values. This information is sent by SQL Server after ResultSet data.

[codecov-io]

Codecov Report

Merging #785 into dev will increase coverage by 0.02%.
The diff coverage is 52.94%.

@@             Coverage Diff              @@
##                dev     #785      +/-   ##
============================================
+ Coverage     48.16%   48.18%   +0.02%     
+ Complexity     2785     2782       -3     
============================================
  Files           116      116              
  Lines         27858    27862       +4     
  Branches       4639     4641       +2     
============================================
+ Hits          13418    13426       +8     
+ Misses        12230    12208      -22     
- Partials       2210     2228      +18

Flag	Coverage Δ	Complexity Δ
#JDBC42	47.65% <52.94%> (+0.05%)	2736 <0> (-3)	⬇️
#JDBC43	48.1% <52.94%> (+0.04%)	2776 <0> (-2)	⬇️

Impacted Files	Coverage Δ	Complexity Δ
...m/microsoft/sqlserver/jdbc/SQLServerResultSet.java	32.54% <0%> (-0.2%)	254 <0> (-2)
...oft/sqlserver/jdbc/SQLServerPreparedStatement.java	52.23% <50%> (ø)	217 <0> (ø)	⬇️
...m/microsoft/sqlserver/jdbc/SQLServerStatement.java	59.71% <66.66%> (-0.06%)	136 <0> (ø)
...ava/com/microsoft/sqlserver/jdbc/ScrollWindow.java	67.9% <0%> (-4.94%)	16% <0%> (-1%)
...om/microsoft/sqlserver/jdbc/ReaderInputStream.java	45.05% <0%> (-4.4%)	16% <0%> (-1%)
...om/microsoft/sqlserver/jdbc/SimpleInputStream.java	51.47% <0%> (-1.48%)	11% <0%> (-1%)
...c/main/java/com/microsoft/sqlserver/jdbc/Util.java	60.25% <0%> (-0.44%)	87% <0%> (-1%)
...om/microsoft/sqlserver/jdbc/SQLServerBulkCopy.java	52.6% <0%> (-0.12%)	262% <0%> (-1%)
...rc/main/java/com/microsoft/sqlserver/jdbc/dtv.java	62.55% <0%> (+0.23%)	0% <0%> (ø)	⬇️
... and 4 more

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[peterbae]

add brackets even if there's only one line in the if statement

[peterbae]

Modify javadoc now that clearFlag is a parameter

[cheenamalhotra]

Done