feat: improve error message for typo in IF NOT EXISTS

[tisonkun]

I hereby agree to the terms of the GreptimeDB CLA.

Refer to a related PR or issue link (optional)

What's changed and what's your intention?

This closes #3471.

Result:

public=> CREATE TABLE IF NOT EXIST t();
ERROR:  Unexpected token while parsing SQL statement: CREATE TABLE IF NOT EXIST t();, expected: 'EXISTS', found: EXIST: sql parser error: Expected EXISTS, found: EXIST at Line: 1, Column 21
public=> CREATE TABLE IF NOT t();
ERROR:  Unexpected token while parsing SQL statement: CREATE TABLE IF NOT t();, expected: 'EXISTS', found: t: sql parser error: Expected EXISTS, found: t at Line: 1, Column 21
public=> CREATE TABLE IF EXISTS t();
ERROR:  SQL statement is not supported: CREATE TABLE IF EXISTS t();, keyword: EXISTS
public=> CREATE TABLE IF EXIST t();
ERROR:  Missing time index constraint
public=> CREATE TABLE t();
ERROR:  Missing time index constraint
public=> CREATE TABLE t(ts TIMESTAMP TIME INDEX);
OK 0
public=> CREATE TABLE IF();
ERROR:  Missing time index constraint
public=> CREATE TABLE IF(ts TIMESTAMP TIME INDEX);
OK 0
public=> DROP TABLE t;
OK 0
public=> DROP TABLE IF;
OK 0

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR does not require documentation updates.

[codecov]

Codecov Report

Attention: Patch coverage is 83.87097% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 85.32%. Comparing base (e410192) to head (0c4282d).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3817      +/-   ##
==========================================
- Coverage   85.60%   85.32%   -0.29%     
==========================================
  Files         955      955              
  Lines      163104   163125      +21     
==========================================
- Hits       139625   139181     -444     
- Misses      23479    23944     +465     

[killme2008]

Could you add some sqlness cases?

[tisonkun]

@killme2008 added. The sample queries above are added as a new sqlness case create_if_not_exists.sql