feat: add net.CIDR_netmask function

[johngmyers]

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

• N
• Y

fixes #1857

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

kclvm/runtine/src/net

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

Adds a function to calculate the netmask of an IPv4 CIDR

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 14530872212

Details

• 49 of 73 (67.12%) changed or added relevant lines in 2 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.07%) to 70.599%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
kclvm/runtime/src/net/mod.rs	48	72	66.67%

Files with Coverage Reduction	New Missed Lines	%
kclvm/sema/src/advanced_resolver/node.rs	1	84.97%

Totals
Change from base Build 14528394708:	0.07%
Covered Lines:	53710
Relevant Lines:	76078

---

💛 - Coveralls

[He1pa]

Is this PR still in draft status or has it been completed?

[johngmyers]

This was blocked on #1920. Now it's merged, I rebased and marked ready for review.

I'm now putting together a documentation PR.

[zong-zhe]

LGTM