fix: improve the loading bot performance

[lei9444]

Description

issue

1. The lg files are parsed twice
2. composer will wait for all resources process to finish

for calendar skill, parsing time is 19s, some other tasks' (render, state set) time is 3s, the total time to finish is 22s

fix

1. reduce one lg files' index. move all parsing operations to the worker.
2. put the lg files index to background. If we open a new dialog, check the lg file state and do a single parse if the file is not yet parsed during the loading stage.

The total time now to show the design page is about 5s

next step
If this solution is ok, we can let lu and qna use the same solution during loading.

Task Item

refs #5708

Screenshots

[coveralls]

Coverage increased (+0.1%) to 52.908% when pulling 3d6f212 on lei9444:loadtime into c68205a on microsoft:main.

[zhixzhan]

Tested on my side, looks good!