rollback sql-hint and rewrite schema autocomplete

[azmy60]

I didn't realize we could autocomplete the schema with the original sql-hint file.

sql-hint is now reverted to this commit.

todos:

• fork tests from cm5 repo, add additional tests such as:
  • must be able to autocomplete alias when using quotes on the table (e.g. select t.<column> from "MyTable" as t)
• fix text/x-pgsql mode for postgres to allow " (double quotes) instead of ` (backticks) on identifiers or use test/x-sqlite mode temporarily (look at codemirror5/mode/sql/sql.js)
• in postgres, alias shouldn't be quoted. The fix is not from sql-hint, but it's possible?, also look at codemirror5/mode/sql/sql.js

closes #1720

[azmy60]

This was tested using postgres. I'm gonna need to test other databases and some edge cases too. I'm expecting there is not gonna be a lot of other changes after this.

[rathboma]

@azmy60 what's the status of this PR, is it ready for review again? (only 3/4 tasks are marked as 'done')

[azmy60]

Oh sorry, I forgot to tell you I couldn't find the solution to the 4th one yet. It is not from the autocomplete.

But it's ready for review if we want to ignore that for now 😆.

Note: it happens only in postgres (using "text/x-pgsql" mode). So it must have the deal with the mode module, not the autocomplete or sql-hint.