feature: mysql 5.x and 8.x jdbc drivers coexist in the server

[ggndnn]

Ⅰ. Describe what this PR did

This PR provided a feature that mysql 5.x and 8.x jdbc drivers coexist in the server to fix issues like #2116.

1. Made use of DriverClassLoader to load mysql 5.x and 8.x driver separately.
2. Moved mysql driver jar from classpath to special location that the mysql drivers can coexist.
3. Upgraded dbcp to avoid loading error (https://issues.apache.org/jira/browse/DBCP-333).
4. Determined different drivers according to driverClassName:

store.db.driverClassName=com.mysql.jdbc.Driver -> mysql 5.x
store.db.driverClassName=com.mysql.cj.jdbc.Driver -> mysql 8.x

5. Tested following combinations:

dbcp + mysql-connector-java-5.1.30
dbcp + mysql-connector-java-8.0.19
druid + mysql-connector-java-5.1.30
druid + mysql-connector-java-8.0.19

Ⅱ. Does this pull request fix one issue?

Ⅲ. Why don't you add test cases (unit test/integration test)?

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[codecov-io]

Codecov Report

Merging #2328 into develop will increase coverage by 0.15%.
The diff coverage is 10.25%.

@@              Coverage Diff              @@
##             develop    #2328      +/-   ##
=============================================
+ Coverage       51.6%   51.76%   +0.15%     
- Complexity      2693     2695       +2     
=============================================
  Files            517      517              
  Lines          16734    16752      +18     
  Branches        2039     2033       -6     
=============================================
+ Hits            8636     8672      +36     
+ Misses          7290     7270      -20     
- Partials         808      810       +2

Impacted Files	Coverage Δ	Complexity Δ
...ata/core/store/db/AbstractDataSourceGenerator.java	0% <0%> (ø)	0 <0> (ø)	⬇️
...eata/server/store/db/DruidDataSourceGenerator.java	100% <100%> (+100%)	2 <0> (+2)	⬆️
...seata/server/store/db/DbcpDataSourceGenerator.java	100% <100%> (+100%)	2 <0> (+2)	⬆️
...o/seata/server/coordinator/DefaultCoordinator.java	54.35% <0%> (-0.52%)	28% <0%> (-1%)
...in/java/io/seata/server/session/GlobalSession.java	84% <0%> (-0.45%)	72% <0%> (-1%)

[slievrly]

[slievrly]

1. IDE(AppClassLoader)+ mysql5 + commit/rollback as expected
2. IDE(AppClassLoader)+ mysql8 + commit/rollback as expected
3. distribute pkg(URLClassLoader)+ mysql5 + commit/rollback as expected
4. distribute pkg(URLClassLoader)+ mysql8 + commit/rollback as expected

[l81893521]

LGTM. Test passed.

dbcp + mysql5
dbcp + mysql8
druid + mysql5
druid + mysql8