Fix saving of prayer points & hitpoints

What has been done in this MR?

• Hitpoints and prayer points are now saved separately, rather than incorrectly as dynamic levels for their respective skills.
  • Fixes #1927
  • The game now no longer complains about missing requirements if you log in with non-full hitpoints or prayer points. (This change only takes effect after you have logged out at least once after this MR has been pushed to prod.)
• Removed dead code, i.e. an unused parse method, in the player save loader

What should testers check?

Nothing, this has been unit-tested. However, this MR should not be merged to master until !1799 has been, since that is the MR that actually bumps the save version to 2.

• I have tested these changes thoroughly.
• I used the relevant Zaros tool for any JSON edits where possible, and have attached screenshots of any changes.