Make ResultSetMetaData accessible when ResultSet is closed

[ulvii]

According to JDBC specs (15.2.5) - ResultSetMetaData instances that were created by a ResultSet that has been closed are still accessible. Removing checkClosed() from SQLServerResultSetMetaData. Fix for #678.

[codecov-io]

Codecov Report

Merging #685 into dev will increase coverage by 0.04%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##                dev    #685      +/-   ##
===========================================
+ Coverage     48.06%   48.1%   +0.04%     
- Complexity     2571    2574       +3     
===========================================
  Files           112     113       +1     
  Lines         26582   26561      -21     
  Branches       4436    4435       -1     
===========================================
+ Hits          12777   12778       +1     
+ Misses        11667   11658       -9     
+ Partials       2138    2125      -13

Flag	Coverage Δ	Complexity Δ
#JDBC42	48.04% <ø> (?)	2571 <ø> (?)
#JDBC43	47.99% <ø> (-0.07%)	2566 <ø> (-5)

Impacted Files	Coverage Δ	Complexity Δ
...oft/sqlserver/jdbc/SQLServerResultSetMetaData.java	38.21% <ø> (-2.73%)	23 <0> (-1)
...rc/main/java/com/microsoft/sqlserver/jdbc/dtv.java	63.17% <0%> (-0.31%)	0% <0%> (ø)
...c/main/java/com/microsoft/sqlserver/jdbc/Util.java	60.91% <0%> (-0.22%)	88% <0%> (-1%)
...in/java/com/microsoft/sqlserver/jdbc/IOBuffer.java	54.59% <0%> (-0.04%)	0% <0%> (ø)
...om/microsoft/sqlserver/jdbc/SQLServerBulkCopy.java	52.48% <0%> (ø)	239% <0%> (ø)	⬇️
.../com/microsoft/sqlserver/jdbc/SQLServerJdbc42.java	40% <0%> (ø)	0% <0%> (?)
...m/microsoft/sqlserver/jdbc/SQLServerResultSet.java	32.78% <0%> (+0.07%)	242% <0%> (+1%)	⬆️
...n/java/com/microsoft/sqlserver/jdbc/DataTypes.java	78.01% <0%> (+0.16%)	5% <0%> (+1%)	⬆️
...oft/sqlserver/jdbc/SQLServerPreparedStatement.java	50.85% <0%> (+0.24%)	157% <0%> (ø)	⬇️
.../microsoft/sqlserver/jdbc/SQLServerDataSource.java	45.66% <0%> (+0.26%)	66% <0%> (ø)	⬇️
... and 5 more

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