fix(bitswap): simplify SessionInterestManager

[guillaumemichel]

Follow up to #752

After investigating around 6cd1ed9, I found that SessionInterestManager keeping track of Interested session, doesn't have a single use case, as @Wondertan suggested.

SessionInterestManager is recording a session's wants (blocks that we want, and that we didn't get yet), as well as interests (block that we want, and we have already). SessionsInterestManager isn't doing anything about the interests, hence I removed interests tracking altogether.

cc: @gammazero

[gammazero]

Thanky for following up in this. Couple of comments to fix, now that there is no distinction between wants and interests.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 60.46%. Comparing base (5c158ec) to head (89f11ca).
Report is 1 commits behind head on main.

@@           Coverage Diff           @@
##             main     #821   +/-   ##
=======================================
  Coverage   60.46%   60.46%           
=======================================
  Files         244      244           
  Lines       31100    31081   -19     
=======================================
- Hits        18805    18794   -11     
+ Misses      10617    10607   -10     
- Partials     1678     1680    +2     

Files with missing lines	Coverage Δ
...l/sessioninterestmanager/sessioninterestmanager.go	100.00% <100.00%> (ø)
...p/client/internal/sessionmanager/sessionmanager.go	95.78% <100.00%> (ø)

... and 8 files with indirect coverage changes