Improve interface between compiler and symtable

In this issue I want to try and improve the interface between the compiler and the symtable.

Problems I see are:

• the compiler modifies the symtable
• the compiler performs calculations that the symtable could do (such as in push_inlined_comprehension_state)
• the symtable is actually not a correct representation of some scopes, like those of inlined comprehensions (the comprehension scope it removed from the symtable tree, but is still access from the compiler via the symtable dict). Exception handlers are another example of scope changes that the compiler does, which are not reflected in the symtable.

Linked PRs

• gh-122986

まず compiler と symtable の実装を読み、push_inlined_comprehension_state と、inlined comprehensions および exception handler の処理に注目します。compiler が symtable を変更せず、symtable が所有する計算をそこへ移し、スコープの変更が一貫して表現される、より明確なインターフェースを確立できれば完了です。