chore(compiler): improve performance for isolatedModules: false

[ahnpnl]

Summary

Improve performance for isolatedModules: false by only creating LanguageService instance with limited amount of initial files.

Because when creating LanguageService instance with fileNames from tsconfig, often this fileNames includes all the files in the project which makes internal TypeScript performs scanning and reading the unnecessary files. This is not optimal because it will create lots of I/O threads which then impact heavily on the performance.

This PR should help #1115 and all related performance issues by somewhere around 30% improvement in speed.

Test plan

Green CI

Does this PR introduce a breaking change?

• Yes
• No

Other information

N.A.

[coveralls]

Pull Request Test Coverage Report for Build 4504

• 48 of 48 (100.0%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.05%) to 92.893%

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Totals
Change from base Build 4502:	0.05%
Covered Lines:	1074
Relevant Lines:	1109

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💛 - Coveralls