Cleanup session managers to encapsulate & defer better

[Grazfather]

gef.session points to a session manager and keeps state, but was often referencing gef.session instead of self. Also, some checks for remote sessions were unnecessary: Since the session has a remote attribute, callers on the session can count on the session manager to provide the correct data/function

[github-actions]

🤖 Coverage update for 8822e39 🟢

	Old	New
Commit	c17a0d2	8822e39
Score	71.5816%	71.5844% (0.0028)

[github-actions]

🤖 Coverage update for 8822e39 🔴

	Old	New
Commit	c17a0d2	8822e39
Score	71.5816%	71.5623% (-0.0193)