Generate UIDs for AST nodes with Expression base class

[HoundThe]

I've added UIDGenerator as part of the ParserDriver, which assigns UIDs to AST nodes that have class Expression as their base class.

The UIDs are supposed to be unique for a given input and deterministic, they are implemented using a 64bit resettable counter. The counter is reset when new parsing input is provided using the existing prepareParser() function and when the condition rule is applied, so it's reset before parsing each condition.

I've modified the existing rule condition AST dumper example code, to print the UIDs and for input:

rule ExampleRule
{
    strings:
        $my_text_string = "text here"
        $my_hex_string = { E2 34 A1 C8 23 FB }
        $a = "text1"
    condition:
        $my_text_string or $my_hex_string and
		not $a or false
}

rule ExampleRule1
{
    strings:
        $my_text_string = "text here" private
        $my_hex_string = { E2 34 A1 C8 23 FB }
        $a = "text1"
        $b = "text2"
        $c = "text3"
        $d = "text4"
    condition:
        ($a or $b) and ($c or $d)
        or (#a == 6 and #b > 10) and
        any of them
}

I get the following output:

==== RULE: ExampleRule
Or[0x55c587337c60]  uid=7
    Or[0x55c587335840]  uid=5
        String[0x55c587318880]  id=$my_text_string uid=0
        And[0x55c5873357d0]  uid=4
            String[0x55c587334230]  id=$my_hex_string uid=1
            Not[0x55c587332890]  uid=3
                String[0x55c587335720]  id=$a uid=2
    BoolLiteral[0x55c587337660]  value=false uid=6
==== RULE: ExampleRule1
Or[0x55c587346980]  uid=21
    And[0x55c5873414a0]  uid=8
        Parentheses[0x55c587340bb0]  uid=3
            Or[0x55c587340590]  uid=2
                String[0x55c58731b910]  id=$a uid=0
                String[0x55c587340540]  id=$b uid=1
        Parentheses[0x55c587341430]  uid=7
            Or[0x55c5873411c0]  uid=6
                String[0x55c587340f20]  id=$c uid=4
                String[0x55c587341170]  id=$d uid=5
    And[0x55c587346910]  uid=20
        Parentheses[0x55c587344c20]  uid=16
            And[0x55c587344ab0]  uid=15
                Equal[0x55c587343b40]  uid=11
                    StringCount[0x55c587342f20]  id=#a uid=9
                    IntLiteral[0x55c587343840]  value=6 uid=10
                GreaterThan[0x55c587344a40]  uid=14
                    StringCount[0x55c5873441b0]  id=#b uid=12
                    IntLiteral[0x55c5873449f0]  value=10 uid=13
        Of[0x55c587346870]  uid=19
            Any[0x55c5873464b0]  uid=17
            Them[0x55c587346820]  uid=18

[metthal]

Could we please also mention this in a documentation in docs folder which is then getting generated for our ReadTheDocs? Otherwise, looks good and I think this would suffice.

[HoundThe]

Thanks a lot for the review! I've incorporated the feedback.