optimize: optimize about ConfigFuture (#2013)

[ph3636]

Describe what this PR did?
In the ConfigFuture class, it is currently implemented using CountDownLatch.
This synchronization method is relatively heavy, we should replace it with CompletableFuture to achieve.

Will not change the ConfigFuture API
Consider that the server will process a large number of Messages in the future, and the Get mode of the CompletableFuture will perform better when testing a large number of messages.

[codecov-io]

Codecov Report

Merging #2018 into develop will not change coverage.
The diff coverage is 40%.

@@            Coverage Diff            @@
##             develop   #2018   +/-   ##
=========================================
  Coverage       55.1%   55.1%           
- Complexity      2473    2474    +1     
=========================================
  Files            444     444           
  Lines          14758   14758           
  Branches        1743    1742    -1     
=========================================
  Hits            8132    8132           
- Misses          5881    5884    +3     
+ Partials         745     742    -3

Impacted Files	Coverage Δ	Complexity Δ
...ain/java/io/seata/core/protocol/MessageFuture.java	83.33% <100%> (-0.67%)	10 <0> (-1)
...re/src/main/java/io/seata/config/ConfigFuture.java	45.83% <33.33%> (-3.11%)	8 <1> (ø)
...o/seata/server/coordinator/DefaultCoordinator.java	48.41% <0%> (+0.39%)	28% <0%> (+1%)	⬆️
...in/java/io/seata/server/session/GlobalSession.java	85.02% <0%> (+0.48%)	68% <0%> (+1%)	⬆️

[xingfudeshi]

LGTM.

[slievrly]

LGTM