refactor(language-service): rename host to tsLsHost

[ayazhafiz]

Disambiguate the name of the Language Service Host used in constructing
a TypeScript Language Service Host by renaming the host property to
tsLsHost.

PR Checklist

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• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• angular.io application / infrastructure changes
• Other... Please describe:

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

• Yes
• No

Other information

[kyliau]

thank you!

[mhevery]

please resolve conflict.

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