Fix SQLServerDatabaseMetadata.getMaxConnections() API query

[cheenamalhotra]

Currently driver was using sp_configure to fetch 'user connections' configuration which is not correct way to do it. Also with SQL Server 2019, this configuration is moved to 'Advanced Options' hence cannot be run directly as with older SQL Servers.

This PR modifies the query and executes SELECT from sys.configurations which is the recommended way for gathering metadata information.

[codecov-io]

Codecov Report

Merging #1009 into dev will decrease coverage by 0.05%.
The diff coverage is 11.11%.

@@             Coverage Diff             @@
##               dev    #1009      +/-   ##
===========================================
- Coverage       53%   52.94%   -0.06%     
+ Complexity    3149     3140       -9     
===========================================
  Files          119      119              
  Lines        27943    27947       +4     
  Branches      4668     4671       +3     
===========================================
- Hits         14811    14797      -14     
- Misses       10911    10921      +10     
- Partials      2221     2229       +8

Impacted Files	Coverage Δ	Complexity Δ
...soft/sqlserver/jdbc/SQLServerDatabaseMetaData.java	36.99% <11.11%> (+0.17%)	70 <1> (+1)	⬆️
...om/microsoft/sqlserver/jdbc/SimpleInputStream.java	55.97% <0%> (-1.5%)	15% <0%> (-1%)
...a/com/microsoft/sqlserver/jdbc/PLPInputStream.java	59.76% <0%> (-1.19%)	34% <0%> (-1%)
...rc/main/java/com/microsoft/sqlserver/jdbc/DDC.java	47.51% <0%> (-1.08%)	111% <0%> (-2%)
...ncurrentlinkedhashmap/ConcurrentLinkedHashMap.java	38.79% <0%> (-0.44%)	43% <0%> (-1%)
...c/main/java/com/microsoft/sqlserver/jdbc/Util.java	59.69% <0%> (-0.44%)	90% <0%> (-1%)
...m/microsoft/sqlserver/jdbc/SQLServerResultSet.java	44.18% <0%> (-0.2%)	327% <0%> (-3%)
...rc/main/java/com/microsoft/sqlserver/jdbc/dtv.java	68.59% <0%> (-0.12%)	0% <0%> (ø)
...om/microsoft/sqlserver/jdbc/SQLServerBulkCopy.java	51.56% <0%> (-0.07%)	255% <0%> (-1%)
...in/java/com/microsoft/sqlserver/jdbc/IOBuffer.java	61.2% <0%> (+0.13%)	0% <0%> (ø)	⬇️

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