Spike support duplicate column names

[acarbonetto]

Description

PoC created to add support for duplicate column names. Previously an error was thrown.
See discussions here and here.

Examples:

opensearchsql> select 1 AS `a`, 2 AS `a`, 3, 3;
fetched rows / total rows = 1/1
+-----+-----+-----+-----+
| a   | a   | 3   | 3   |
|-----+-----+-----+-----|
| 1   | 2   | 3   | 3   |
+-----+-----+-----+-----+
opensearchsql> select 1+1, 1+1;
fetched rows / total rows = 1/1
+-------+-------+
| 1+1   | 1+1   |
|-------+-------|
| 2     | 2     |
+-------+-------+

Issues Resolved

#785
#1382

Check List

• New functionality includes testing.
  • All tests pass, including unit test, integration test and doctest
• New functionality has been documented.
  • New functionality has javadoc added
  • New functionality has user manual doc added
• Commits are signed per the DCO using --signoff

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For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[MitchellGale]

FYI - you have a file conflict @acarbonetto

[Swiddis]

Is this still in progress? Should we close it?

[Swiddis]

Closing as stale -- feel free to reopen if work is resumed