Post-merge fixes to Node & OS documentation

[Mickeon]

Closes #86813

This PR picks up from #68560 and #80282, adding more details, addressing a few inaccuracies and poor wording.

For Node:

• Adds missing descriptions to the ProcessThreadMessages flag constants, finally filling them all.
• Moves a detail of set_process, set_physics_process etc. into their own note and specifies that they're automatically called before _ready.
• Changes an error in name's description:
  • When the original PR was made, invalid characters were removed from a Node name. As time passed, this behavior was changed but the description was not.
• Clarifies DUPLICATE_SCRIPTS' behavior.
  • I have no idea what the original PR's description meant. It's nonsense, in hindsight.

For OS:

• Adds a note to explain that for OS.read_string_from_stdin(), a console wrapper is necessary in Windows builds, addressing OS.read_string_from_stdin() switches contexts when running without console wrapper from a console. #86813.

I wanted to rewrite all of the Node thread-related descriptions here (when the original PR was made they did not exist yet), but I'm leaving that for another time.

[Mickeon]

Rebased after #82889 .

[akien-mga]

Thanks!