feat: support configurable main_pkg name

[He1pa]

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

• N
• Y

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

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

support configurable main_pkg name

• 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

[Peefy]

I am not sure if this method is feasible, as during the compilation process, there can be two threads simultaneously, one thread modifying main_pkg and the other thread compiling simultaneously, which will achieve the expected results.

[coveralls]

Pull Request Test Coverage Report for Build 8777948997

Details

• 53 of 63 (84.13%) changed or added relevant lines in 22 files are covered.
• 14 unchanged lines in 5 files lost coverage.
• Overall coverage decreased (-0.02%) to 71.389%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
kclvm/query/src/override.rs	0	3	0.0%
kclvm/sema/src/core/symbol.rs	0	3	0.0%
kclvm/ast/src/lib.rs	3	7	42.86%

Files with Coverage Reduction	New Missed Lines	%
kclvm/tools/src/LSP/src/request.rs	1	72.02%
kclvm/ast/src/token.rs	1	58.9%
kclvm/sema/src/builtin/option.rs	1	0.0%
kclvm/config/src/settings.rs	4	78.26%
kclvm/ast/src/config.rs	7	0.0%

Totals
Change from base Build 8763607955:	-0.02%
Covered Lines:	52622
Relevant Lines:	73712

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💛 - Coveralls