### _Why are the changes needed?_
To fix the config name and placeholder with `username` introduced in https://github.com/apache/incubator-kyuubi/pull/3235 violate this convention as in JDBC driver use `user` keyword used for connection user rather than `username`,
1. change config name from `kyuubi.authentication.jdbc.username` to `kyuubi.authentication.jdbc.user`
2. change placeholder from `${username}` to `${user}`
3. update docs and config description related to above changes, and sync the update in jdbc auth docs statement details to config docs.
4. fix error in throwing AuthenticationException with auth db password. ut added for the fix.
5. other minor update in docs of custom auth
### _How was this patch tested?_
- [x] Add some test cases that check the changes thoroughly including negative and positive cases if possible
- [ ] Add screenshots for manual tests if appropriate
- [x] [Run test](https://kyuubi.apache.org/docs/latest/develop_tools/testing.html#running-tests) locally before make a pull request
Closes#3288 from bowenliang123/jdbc-auth-config-update.
Closes#3222
502703fb [Bowen Liang] skip map for placeholder value lookup
3733be41 [liangbowen] nit
ab00525b [liangbowen] nit
2301c4f0 [liangbowen] fix ut of jdbc auth with wrong_password
06f0c1bb [liangbowen] remove redundant docs
ec4565b3 [liangbowen] remove redundant docs
ae1cce2e [liangbowen] fix compilation error of configLog
5d14103b [liangbowen] simplify configLog
6678e657 [liangbowen] reformat
52c1038e [liangbowen] simplify placeholder checking
21c2d5ea [liangbowen] check whether placeholders in supported list before conn establishment or authenticate
7db0adf5 [liangbowen] ut for unknown placeholder
657de6af [liangbowen] nit
736b3f22 [liangbowen] refactoring placeholder value lookup, for preventing setString multiple times with "i+1"
86c89125 [liangbowen] setMaxRows after prepare placeholder, to postpone operation on jdbc conn
115fae50 [liangbowen] increase test code coverage
b45b28cb [liangbowen] resultSet returned by executeQuery is never null
e1c07274 [liangbowen] update ut for redactPassword in JdbcUtils
b4a52e29 [liangbowen] fix typo in docs of custom auth
371c2c6e [liangbowen] move redactPassword method to JdbcUtils and add ut.
a4973c59 [liangbowen] reformat code
486e1503 [liangbowen] fix error in throwing AuthenticationException with auth db password. add ut for the fix.
efced90a [liangbowen] update settings.md
ef97e354 [liangbowen] add SELECT prefix hint for doc of kyuubi.authentication.jdbc.query
025f94c7 [liangbowen] fix username to user in JdbcAuthenticationProviderImpl by 1. use config name `kyuubi.authentication.jdbc.user`, 2. use ${user} placeholder instead of ${username}
Lead-authored-by: liangbowen <liangbowen@gf.com.cn>
Co-authored-by: Bowen Liang <liangbowen@gf.com.cn>
Signed-off-by: Cheng Pan <chengpan@apache.org>
8b65e0e435