Dissolve schema query into distinct ToDataTable paths

[atifaziz]

This is a refactoring PR that improves ToDataTable.

The internal BuildOrBindSchema method created a schema projection (schemas), but the two paths taken by the code (based on whether the table had columns) accessed distinct parts of the projection. This PR removes the query to save on allocation costs, moves the only shared bit into a new local function called GetElementaryTypeOfPropertyOrField and the rest is dissolved into each code path.

[codecov]

Codecov Report

Merging #1007 (0f599d6) into master (f766827) will decrease coverage by 0.02%.
The diff coverage is 100.00%.

❗ Current head 0f599d6 differs from pull request most recent head b9c3062. Consider uploading reports for the commit b9c3062 to get more accurate results

@@            Coverage Diff             @@
##           master    #1007      +/-   ##
==========================================
- Coverage   92.59%   92.57%   -0.02%     
==========================================
  Files         113      113              
  Lines        3430     3422       -8     
  Branches     1054     1055       +1     
==========================================
- Hits         3176     3168       -8     
  Misses        191      191              
  Partials       63       63              

Impacted Files	Coverage Δ
MoreLinq/ToDataTable.cs	96.51% <100.00%> (-0.30%)	⬇️

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