Add unit-test for LRM 3.0 Section 8.7 "Bit sizes for numeric expressions"

[LeeKaiXuan]

Rules

Expression	Bit size	Comments
Unsized constant number	At least 32	Suggest 65 bits
Sized constant number	As specified
i op j, where op is: + - * / % & | ^	max(L(i),L(j))
op i, where op is: + - ~	L(i)
op i, where op is: & | ^	1
i op j, where op is: >> << **	L(i)	j is self-determined
i ? j : k	max(L(j),L(k))	i must be Boolean
cast, where casting_type is an integer type	L(casting_type)

• Unsized unbased decimal and octal numbers are signed.
• Unsized unbased hexadecimal numbers are unsigned.
• Based numbers are unsigned, except when they are designated as signed with the 's notation (e.g., 4'sd12).
• Bit-select results are unsigned, regardless of the operands.
• Part-select results are unsigned, regardless of the operands, even if the part-select specifies the entire width.
• If any context-determined operand of an expression is unsigned, the result is unsigned regardless of the operators.
• If all context-determined operands of an expression are signed, the result is signed regardless of the operators, unless specified otherwise.