Ignore FULLTEXT KEYs in CREATE TABLE statements.

[kolbe]

What problem does this PR solve?

#3658

What is changed and how it works?

FULLTEXT KEY in CREATE TABLE is ignored.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Code changes

• Has exported function/method change
• Has exported variable/fields change
• Has interface methods change
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation
• Need to update the tidb-ansible repository
• Need to be included in the release note

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #9786 into master will decrease coverage by 0.0058%.
The diff coverage is 0%.

@@               Coverage Diff                @@
##             master      #9786        +/-   ##
================================================
- Coverage   67.2278%   67.2219%   -0.0059%     
================================================
  Files           381        381                
  Lines         79839      79843         +4     
================================================
- Hits          53674      53672         -2     
- Misses        21379      21384         +5     
- Partials       4786       4787         +1

[kolbe]

Closing; will create a new PR coming from a fork rather than branch.