Source Pruning for Language Sever Completion

[nadeeshaan]

Description:
Auto-completion is provided most of the time, while the user is typing. During the typing, ballerina source is incorrect with syntax errors. Therefore, when trying to parse the source (in the sense, current package) compiler fails to build the correct source. In order to avoid the compiler failures, either grammar or parser has to optimize for fallback and recover the error. This approach can be error-prone and performance intensive due to the inline context recovery.
In order to avoid complexity, another approach is to prune the source/ remove the erroneous tokens and inject a valid source to the parser.

• Finalize the terminating tokens
• Finalize the token removal rules for grammar
• Implement Token Removal strategy
• Implement Source inject through document manager and Completion context

Affected Versions:
v0.990.3.0