Initialize new isolate after restart

[annagrin]

Dart devtools sometimes gets erroneous isolate information from dwds in the middle of hot restart,
for example, getIsolate does not wait for initializations of the new isolate after restart and returns
an isolate with null ID.

This seems to cause various issues after hot restart, including exceptions in debug console, non-working
layout explorer, and disabled breakpoints in the UI. While this PR does not solve all of them yet, it makes
sure that the new isolate is initialized before VM replies to the clients after hot restart:

• reset initialization completer on destroyIsolate.
• make all supported VM API wait for isolate initialization before proceeding.
• add expression evaluation tests after hot restart.

Towards: flutter/flutter#74903
Closes: #1304

[bkonyi]

LGTM!

[annagrin]

@grouma re-requesting approval after my latest commit - my fix attempt did not work, as shown by windows test failures, where isolate was marked as initialized and expression evaluation was starting before updateDependencies was even called.

Instead, I made evaluate and evaluateInFrame calls wait until expression compiler is created, initialized, and dependencies are updated, which can be only done from ChromeProxyService. Reverted my changes in ExpressionCompilerService, as it does not have enough information to make sure we compile expressions after dependency updates.