CLI: Fixed crash when replacing event scripts, slight refactor

[TheAwoo]

Description

When trying to replace an event script in a non-undertale title, one is met with an exception:

UndertaleModCli replace data.orig
-c gml_Object_obj_light_controller_Draw_0=./Mods/gml_Object_obj_light_controller_Draw_0.gml
-v -o data.win

System.InvalidCastException: Unable to cast object of type 'UndertaleModLib.Models.EventType' to type 'System.Int32'.
   at UndertaleModCli.Program.ImportCode(String codeName, String gmlCode, Boolean isGML, Boolean doParse, Boolean destroyASM, Boolean checkDecompiler, Boolean throwOnError) in /mnt/nex/projekty/undertale-mod-tool/UndertaleModCli/Program.UMTLibInherited.cs:line 921
   at UndertaleModCli.Program.ImportGMLString(String codeName, String gmlCode, Boolean doParse, Boolean checkDecompiler) in /mnt/nex/projekty/undertale-mod-tool/UndertaleModCli/Program.UMTLibInherited.cs:line 607
   at UndertaleModCli.Program.ReplaceCodeEntryWithFile(String codeEntry, FileInfo fileToReplace) in /mnt/nex/projekty/undertale-mod-tool/UndertaleModCli/Program.cs:line 664
   at UndertaleModCli.Program.Replace(ReplaceOptions options) in /mnt/nex/projekty/undertale-mod-tool/UndertaleModCli/Program.cs:line 416
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
   at System.Reflection.MethodInvoker.Invoke(Object obj, IntPtr* args, BindingFlags invokeAttr)

The following commits fix the issue and introduce enhancements:

• Plain cast to int has been substituted to a Convert.ToInt32 call which does not fault,
• Removed needless reflection (which would also fault on call) when trying to obtain a particular value from an enum.

Caveats

Hopefully none, the changes introduced shouldn't change any behaviour, just the value handling.

Notes

Game used: ZERO Sievert
Tested on a Linux box:

awoo@~ $ uname -a
Linux [redacted] 6.1.9-zen1-2-zen #1 ZEN SMP PREEMPT_DYNAMIC Sat, 04 Feb 2023 23:45:10 +0000 x86_64 GNU/Linux