* implicit-casts:false on flutter_tools

* use castStringKeyedMap

* address review comments

* address review comments

* fix issues after rebase

Removes multiple re-entrant calls of bundle and aot and replaces them with a single call to assemble. This restores full caching and will allow follow-up performance improvements when building multiple ABIs

Fixes various Flutter framework test failures when bytecode is enabled.

Bytecode generation will otherwise omit prologue code, causing --causal-async-stacks passed to the VM to behave inconsistently.

Bytecode generation will otherwise omit assert code, causing --enable-asserts to have no effect in the VM.

This reverts commit 5e7beaf7.

This reverts commit 202c1b42.

Move tools tests into a general.shard directory in preparation to changing how we shard tools tests (#36108)