The patch adopts and reuses the optimizations from the legacy backend.
The optimizations remove useless temporary variables,
statements and simplify generated JS code.
The optimizations can be disabled by `-Xoptimize-generated-js=false`.
Related to KT-51139
Namely:
- Generate debug info for closing braces, which allows the breakpoints
set on closing braces to be hit
- Generate debug info for 'if' and 'try/catch' statements.
KT-46276
Temporary variable loads in when expressions had the offsets
of the variable declaration. That leads to hacks during codegen
for line number generation.
Instead of those hacks, give the variable loads the offsets of
the context in which they occur. That avoids the codegen hacks
and fixes stepping behavior for more when expressions.
Alexander Korepanov