Fix module-level alignment breaking after non-alignable constructs

[dannyoler]

Summary

• AlignModuleItems was the only alignment function that did not split partitions by blank lines before classifying groups
• When a non-alignable construct (e.g. module instantiation, macro call) appeared in the module body, GetConsecutiveModuleItemGroups returned kNoMatch, permanently breaking alignment for all subsequent assign statements and declarations in that scope
• Added GetModuleItemGroupsBetweenBlankLines which first partitions by blank lines, then runs GetConsecutiveModuleItemGroups within each sub-range — matching the pattern used by every other alignment function

Before

    assign short_a            = 1;  // aligned
    assign really_long_name_b = 2;  // aligned
    inst #() u (.Z(z));             // breaks alignment permanently
    assign c = 3;                   // NOT aligned
    assign longer_d = 4;            // NOT aligned

After

    assign short_a            = 1;  // aligned (group 1)
    assign really_long_name_b = 2;  // aligned (group 1)
    inst #() u (.Z(z));             // ends group 1, does not affect group 2
    assign c        = 3;            // aligned (group 2)
    assign longer_d = 4;            // aligned (group 2)

Blank lines continue to separate alignment groups as expected. Also removes the resolved TODO(b/161814377) comment.

Test plan

• Verified on a 7400-line production RTL file with module instantiations, DFF macros, and hundreds of assign statements
• Small test case confirms: instantiations don't break alignment, blank lines do break alignment
• Existing verible tests should pass (alignment functions for ports, structs, enums, etc. already use blank-line splitting)

Related issues: #2021, #2481

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: dannyoler / name: Danny Oler (13fba42)

[hzeller]

Thanks for your contribution. Sorry for the delay, was swamped with other projects and missed the mail from github about the change.

Can you have a look at the tests and make them all pass ?
(you probably also have to rebase)