fix(inspector): avoid double RefCell borrow

[bartlomieju]

Fixing some of the fall out from #1193.

Testing in CLI it turned out that there's a double RefCell borrow panic occuring,
when running the REPL - when the exception was raised when evaluating an expression -
and said expression was evaluated as part of dispatching an inspector message

• the op_dispatch_exception op was called that tries to mutable borrow the
  inspector instance.

This is now avoided by storing SessionContainer in the LocalInspectorSession,
instead of JsRuntimeInspector.

This will be further simplified in follow up PRs like #1192.

[nathanwhit]

LGTM

[codecov-commenter]

Codecov Report

❌ Patch coverage is 54.54545% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.56%. Comparing base (0c7f83e) to head (cbc72f4).
⚠️ Report is 336 commits behind head on main.

Files with missing lines	Patch %	Lines
core/inspector.rs	54.54%	15 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1195      +/-   ##
==========================================
- Coverage   81.43%   79.56%   -1.88%     
==========================================
  Files          97      100       +3     
  Lines       23877    25840    +1963     
==========================================
+ Hits        19445    20560    +1115     
- Misses       4432     5280     +848     

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