Add test case for embedded value selects

[emcfarlane]

Adds a testcase for embedded fields when selecting multiple row values. Current behaviour returns the last row value for the embbed ptr to all the structs.

What did this pull request do?

Adds a testcase currently. Looking into the issue.

--- FAIL: TestEmbeddedStruct (0.01s)
    embedded_struct_test.go:92: 0 &{ George }
    embedded_struct_test.go:94: expected author Edward got George
    embedded_struct_test.go:92: 1 &{ George }

User Case Description

Fix embedded struct ptrs. Reverted the optimisation for reusing structs here: #5388

[emcfarlane]

Fixes #5575 and #5838