Add label offset arithmetic in the parser

[lupino3]

Discussed in #714

^{Originally posted by krisutofu October 30, 2022}
Dear EduMIPS64 developers,
thank you for all your work to provide this improved educational simulator. I recently discovered EduMIPS64. I would like to switch to WinMIPS64 but I am missing a good feature that was available in WinMIPS64.

WinMIPS64 allows you to write

    l.d f0, array+0($zero)
    l.d f1, array+8($zero)
    l.d f2, array+16($zero)

It means, it will statically add 0, 8 or 16 to the immediate value that the label is substituted with.

edumips64/src/main/java/org/edumips64/core/parser/Parser.java

Line 676 in 4e61be8

} else if (type == 'L') {

The expression could support up to 5 operators + , - , *, / and % but should support at least + and - or specifically label+imm or label-imm.