make more convinient for developing in the remote machine

[baurine]

When a user develops TiDB dashboard in a remote machine and accesses the frontend page in the local, he will get the following error by accessing http://{remote_addr}:3001/dashboard in the local browser:

Because the frontend can't access the backend API by http://127.0.0.0:12333/dashboard/api.

Solutions:

1. Forward local port 12333 to the remote, for example: ssh -L 12333:locahost:12333 remote_addr.

2. Run TiDB dashboard backend by bin/tidb-dashboard --host 0.0.0.0 and set REACT_APP_DASHBOARD_API_URL=http://{remote_addr}:12333 in the .env file

3. Run TiDB dashboard backend by bin/tidb-dashboard --host 0.0.0.0 and use http://${window.location.hostname}:12333/dashboard instead of http://127.0.0.01:12333/dashboard as API addr prefix.

This PR implements solution 3, and I think this would bring a little more convenience for the developers to develop in a remote machine.

[ti-chi-bot]

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[codecov-commenter]

Codecov Report

Merging #1132 (f9d9a72) into master (4a262b3) will decrease coverage by 1.18%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #1132      +/-   ##
==========================================
- Coverage   29.42%   28.24%   -1.19%     
==========================================
  Files         210      227      +17     
  Lines       11877    12841     +964     
  Branches      647      647              
==========================================
+ Hits         3495     3627     +132     
- Misses       8243     9064     +821     
- Partials      139      150      +11     

Flag	Coverage Δ
be_integration_test_latest	6.88% <ø> (?)
be_integration_test_v4.0.1	6.88% <ø> (?)
be_unit_test	24.00% <ø> (ø)
e2e_test	46.88% <0.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
ui/lib/client/baseUrl.ts	63.63% <0.00%> (ø)
pkg/utils/topology/topology.go	0.00% <0.00%> (ø)
pkg/utils/version/version.go	0.00% <0.00%> (ø)
pkg/config/dynamic_config_manager.go	0.00% <0.00%> (ø)
pkg/utils/topology/pd.go	0.00% <0.00%> (ø)
pkg/utils/topology/store.go	0.00% <0.00%> (ø)
pkg/utils/fx.go	0.00% <0.00%> (ø)
pkg/utils/topology/monitor.go	0.00% <0.00%> (ø)
pkg/apiserver/slowquery/service.go	0.00% <0.00%> (ø)
pkg/config/dynamic_config.go	0.00% <0.00%> (ø)
... and 8 more

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[breezewish]

Nice trick!