feat: Implement AV evasion techniques (section renaming and padding)

This commit introduces two new AV evasion techniques:
- Section renaming: UPX0, UPX1, and UPX2 sections are now renamed to .text, .data, and .rdata respectively.
- Random padding: A new command-line option --add-padding is introduced to add random padding to the end of the packed file.

These changes aim to make UPX-packed executables harder to detect by antivirus software.

src/options.cpp

@@ -43,6 +43,7 @@ void Options::reset() noexcept {
 #define opt ERROR_DO_NOT_USE_opt // self-protect against using the wrong variable
     Options *const o = this;
     mem_clear(o);
+    o->add_padding = false;
     o->crp.reset();
 
     o->cmd = CMD_NONE;