privilege, executor: add SET ROLE and CURRENT_ROLE support

[imtbkcat]

What problem does this PR solve?

support active role and SET ROLE, CURRENT_ROLE function.

What is changed and how it works?

Create an graph data structure to find relationship between role and user quickly, which is always update as other privilege tables. It will load mysql.role_edges table, and convert relationship to an graph.

When we need to active some roles for current session, we need to check whether these roles has been granted for current user. RoleGraph can finish this task quickly.

SET ROLE is just for set active role for current session, more detail: https://dev.mysql.com/doc/refman/8.0/en/set-role.html

Because set default role is not support yet. some gramma will be added soon.

Check List

Tests

• Unit test

Code changes

• Has exported variable/fields change

Side effects

• Increased code complexity

[jackysp]

Move this line to the third party libs part.

[jackysp]

It is better to add some test cases for this built-in function.

[imtbkcat]

ok

[codecov]

Codecov Report

Merging #9581 into master will decrease coverage by 0.0201%.
The diff coverage is 44.8979%.

@@               Coverage Diff                @@
##             master      #9581        +/-   ##
================================================
- Coverage   67.1706%   67.1505%   -0.0202%     
================================================
  Files           381        381                
  Lines         79956      80053        +97     
================================================
+ Hits          53707      53756        +49     
- Misses        21460      21504        +44     
- Partials       4789       4793         +4

[imtbkcat]

/run-all-tests

[imtbkcat]

PTAL @tiancaiamao

[tiancaiamao]

make(map[string]*auth.RoleIdentity, len(s.RoleList))

[tiancaiamao]

Why protobuf is changed here?

[tiancaiamao]

It's better to use roleList map[string]struct{} here

roleList map[string]struct{}

roleList["xx"] = struct{}{}

if _, ok := roleList["xx"] {
    ...
}

[tiancaiamao]

LGTM

[imtbkcat]

PTAL @jackysp

[imtbkcat]

/run-all-tests

[jackysp]

LGTM