Array/structure assignment patterns

Description of the changes

This MR adds support for named assignment patterns, such as:

logic b [0:1] = '{default: 1'b0};

and

typedef struct packed { logic a, logic b } c_t;
c_t c = '{a: 1'b0, b: 1'b1};

Check-list

• Make sure that a changelog entry is present
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Reviewer check-list

• Make sure that the title describes the changes in the merge request
• Make sure that the description of the changes is relevant and it describes all the changes
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