Support BaseScript.RunContext

[Anaminus]

Repurpose script format aliases to use RunContext instead (lua and luau):

Format	Class (RunContext)
server.lua	Script (Server)
client.lua	Script (Client)
plugin.lua	Script (Plugin)
script.lua	Script (Legacy)
localscript.lua	LocalScript
lua	ModuleScript
modulescript.lua	ModuleScript

A potential way to handle backward-compatibility could be to have legacy behavior for lua formats, and new behavior for luau formats:

Format	Class (RunContext)
server.lua	Script (Legacy)
client.lua	LocalScript
plugin.lua	Script (Legacy)
script.lua	Script (Legacy)
localscript.lua	LocalScript
lua	ModuleScript
modulescript.lua	ModuleScript
server.luau	Script (Server)
client.luau	Script (Client)
plugin.luau	Script (Plugin)
script.luau	Script (Legacy)
localscript.luau	LocalScript
luau	ModuleScript
modulescript.luau	ModuleScript

References:

• https://devforum.roblox.com/t/1938784
• https://robloxapi.github.io/ref/class/BaseScript.html#member-RunContext
• https://robloxapi.github.io/ref/enum/RunContext.html