refactor: reorder function sequence to make it more reasonable

[allencloud]

Signed-off-by: Allen Sun [email protected]

Ⅰ. Describe what this PR did

This pr tries to make container, image, network, volume interface's implementation much more in order. This will make go files much more readable.

In addition, I split two files exec_bridge.go and container_exec.go since they are quite decoupled, I think.

Ⅱ. Does this pull request fix one issue?

none

Ⅲ. Describe how you did it

none

Ⅳ. Describe how to verify it

none

Ⅴ. Special notes for reviews

none

[codecov-io]

Codecov Report

Merging #1296 into master will decrease coverage by 0.09%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##           master    #1296     +/-   ##
=========================================
- Coverage    15.4%   15.31%   -0.1%     
=========================================
  Files         174      176      +2     
  Lines       11026    11014     -12     
=========================================
- Hits         1699     1687     -12     
  Misses       9208     9208             
  Partials      119      119

Impacted Files	Coverage Δ
apis/server/exec_bridge.go	0% <0%> (ø)
apis/server/volume_bridge.go	0% <0%> (ø)	⬆️
apis/server/image_bridge.go	15% <0%> (ø)	⬆️
daemon/mgr/container_exec.go	0% <0%> (ø)
daemon/mgr/container.go	0% <0%> (ø)	⬆️
daemon/mgr/image.go	0% <0%> (ø)	⬆️
daemon/mgr/network.go	3.48% <0%> (ø)	⬆️
daemon/mgr/volume.go	0% <0%> (ø)	⬆️
apis/server/container_bridge.go	0% <0%> (ø)	⬆️
apis/server/network_bridge.go	0% <0%> (ø)	⬆️
... and 3 more

[HusterWan]

LGTM