This commit aims to check the type of distribution column. After this
commit, pg_shard errors out if it cannot work on the distribution column on
table distribution call.

This commit adds regression test for partition column which tests
partition columns which is not eligible for distribution.

This commit add checks to find whether the data type of the partition
column has the required support routines for future select/insert/update
commands.

Add tests with unsupported column types.

This commit aims to improve style of tests.

This commit aims to rename GetSupportRoutine function to
GetSupportFunction. Also, updated related variable names and comments.

This commit aims to apply feedback from @jasonmp85. Basically, change
code flow so that code gets shorter and easier to read. Also, apply
style changes.

This commits includes only some whitespace changes.

Fixed some alignment issues, clarified some comment language, renamed
a variable, and moved error call for range partitioning.