Clickhouse global join

• Replaces PR support clickhouse global keyword in join #1615
• Fixes I use it to analyze clickhouse sql，But there is a problem，Can you show me #1535
• All credits to @julianzlzhang, I just fixed the code style.

Support IF... ELSE... statements with Block()

if (a=b) begin
update table1 set a = 'xx' where b = 'condition1';
update table1 set a = 'xx' where b = 'condition2';
end;
else begin
update table1 set a = 'xx' where b = 'condition1';
update table1 set a = 'xx' where b = 'condition2';
end;

• Fixes Some SQL server syntax does not support parsing #1682 / 1

Support SET statement with UserVariable

set @Flag = 1

• Fixes Some SQL server syntax does not support parsing #1682 / 2
• Fixes Parsing "@@" throws exception #1237

Google Spanner Support
Replaces PR Google Spanner support #1415, all credit goes to @s13o
Re-arranged some recently added Tokens in alphabetical order
Update Keywords

Amend JSONExpression and make it accept Expression beyond Column only

SELECT '{"key": "value"}'::json -> 'key' AS X

• Fixes PostgreSQL JSON arrow operators #1696