integrate concat_ws for memsql and snowflake

[theodosis1989]

What type of PR is this?

• Bug Fix

What does this PR do / why is it needed ?

The current translation of joinStrings from PURE is to the CONCAT method in SQL. In some of the SQL implementations, including MemSQL and Snowflake that are addressed in this MR, the CONCAT method concatenates the variables without a delimiter, and produces null when one the values is null.

Example1: ['A', 'B']->joinStrings('|') in PURE, produces SQL CONCAT('A', 'B', '|') which evaluates to 'AB|'.
Example2: ['A', null]->joinStrings('|') in PURE, produces SQL CONCAT('A', null, '|') which evaluates to NULL.

Fix:
This MR maps the joinStrings for MemSQL and Snowflake to CONCAT_WS instead.
CONCAT_WS concatenates the variables using a delimiter
Example1: ['A', 'B']->joinStrings('|') in PURE, produces SQL CONCAT_WS('|', 'A', 'B') which evaluates to 'A|B'.
Example2: ['A', 'B']->joinStrings('|') in PURE, produces SQL CONCAT_WS('|', 'A', NULL) which evaluates to 'A'.

Which issue(s) this PR fixes:

Fixes #

Other notes for reviewers:

Does this PR introduce a user-facing change?

[github-actions]

Test Results

     763 files       763 suites   1h 7m 18s ⏱️
12 601 tests 12 368 ✔️ 233 💤 0 ❌
15 712 runs  15 461 ✔️ 251 💤 0 ❌

Results for commit 0723dc8.

♻️ This comment has been updated with latest results.

[finos-admin]

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[finos-admin]

This PR is stale because it has been open for 30 days with no activity. Please remove stale label or add any comment to keep this open. Otherwise this will be closed in 5 days.