Dynamically update package.json and readme.md in emitter, clear up files for hlc #3567
Description
1: modular -> modular:
if we disable clean up step and don't set config generate-metadata as true,
we need to dynamically update tshy.exports in package.json like
Azure/azure-sdk-for-js@b356509#diff-07db654769781ada9a242a4c485cd47196fd1470626eee38e24bcbf76c02793fL19-R19
to make build succeed in our emitter.
We also need to update readme.md for mpg if generate-metadata is not set as 'true'
2 hlc ->modular:
In this case, we still need to clean up whole library to convert all the files to modular style