Add in new definitions to definitions.h

[gwillcox-r7]

Add a proper THREADINFOCLASS definition, additional SYSTEM_INFORMATION_CLASS definitions, and a BIG_POOL_INFO definition, along with a few other minor changes.

This is needed for #15834 to contain proper definitions vs having to define things itself manually.

I could add a full definition of SYSTEM_INFORMATION_CLASS in and I do plan to do this eventually, however at 200+ system calls that need to be defined still I think this may take some time and not all of them are needed for this PR to work.

Verification

List the steps needed to make sure this thing works

• Review the code
• Make sure the definition file loads correctly.
• Land me plx 😄

[gwillcox-r7]

Rebased into one commit and removed the BIG_POOL_INFO definition since I'm not 100% sure which one is correct or if I am getting it confused with another definition, and its fine for us to just define it within the exploit for the time being until we can get more clarity on this.

[smcintyre-r7]

Everything looks good to me. I spot checked some of the definitions and made sure that the code still compiles for the previous exploit that needed it.

I'll have this landed shortly.