fix add dsl substr aes_cbc

[hktalent]

PR #2307

=== RUN TestDslExpressions/substr('xxtestxxx',2)
substr('xxtestxxx',2): testxxx
--- PASS: TestDslExpressions/substr('xxtestxxx',2) (0.00s)
=== RUN TestDslExpressions/substr('xxtestxxx',2,6)
substr('xxtestxxx',2,6): test
--- PASS: TestDslExpressions/substr('xxtestxxx',2,6) (0.00s)
=== RUN TestDslExpressions/substr('xxtestxxx',2,-2)
substr('xxtestxxx',2,-2): testx
--- PASS: TestDslExpressions/substr('xxtestxxx',2,-2) (0.00s)

[hktalent]

add dsl substr aes_cbc
for #2243 #2304

[hktalent]

@forgedhallpass @ehsandeep what happened?
thanks

[hktalent]

test fix #2301 code:
https://github.com/hktalent/scan4all/blob/main/test/nuclei/testNuclei.go

[ehsandeep]

@hktalent please push the changes into dev branch instead of master