fix: fix wrong dot and assign complete after special ty

[He1pa]

fix issues about wrong complete after str ty.

a = "1"
# a.   // wrong complete str builtin functions 

schema A:
    a: str
   check:   // wrong complete str builtin functions

1. Does this PR affect any open issues?(Y/N) and add issue references (e.g. "fix #123", "re #123".):

• N
• Y [Enhancement][Track] KCL VSCode IDE extension and lsp enhancement #524

2. What is the scope of this PR (e.g. component or file name):

lsp/completion.rs

3. Provide a description of the PR(e.g. more details, effects, motivations or doc link):

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Other

4. Are there any breaking changes?(Y/N) and describe the breaking changes(e.g. more details, motivations or doc link):

• N
• Y

5. Are there test cases for these changes?(Y/N) select and add more details, references or doc links:

• Unit test
• Integration test
• Benchmark (add benchmark stats below)
• Manual test (add detailed scripts or steps below)
• Other

[coveralls]

Pull Request Test Coverage Report for Build 7112991819

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 87.787%

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Totals
Change from base Build 7112634044:	0.0%
Covered Lines:	2293
Relevant Lines:	2612

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💛 - Coveralls

[Peefy]

I think the fundamental reason for this issue is to complete the content through the current symbol query. In fact, it is necessary to enhance the semantic model within the compiler, e.g., build expression symbols, and query expression symbols instead of adding a trick function option in the LSP crate. cc @He1pa @NeverRaR