Solana provider refactoring

[darkdh]

Remove disconnect handler

We are currently doing it in
https://github.com/brave/brave-core/blob/b2cc506b7d573033e845c771976ba031343edb38/components/brave_wallet/renderer/js_ethereum_provider.cc#L128-L132
and https://github.com/brave/brave-core/blob/b2cc506b7d573033e845c771976ba031343edb38/components/brave_wallet/renderer/js_solana_provider.cc#L188-L192

It's not necessary to do that because mojo would reconnects automatically.

Separate JSSolanaProvider from gin::Wrappable

we make JSSolanaProvider a WeakPtr,
pass that into the new wrappable class as the “delegate”
the new wrappable class just calls the existing methods on JSSolanaProvider after checking for null.
ex.

v8::Local<v8::Value> JSSolanaProviderWrapper::GetPublicKey(gin::Arguments* arguments) {
  if (!delegate)
    return v8::Null(isolate);

  return delegate->GetPublicKey(arguments);
}

Make JSSolanaProvider both gin::Wrappable and RederFrameObserver

Follow DomAutomationController and install it in BraveWalletRenderFrameObserver:: DidClearWindowObject
And then bind brave_wallet::mojom::SolanaProvider in RegisterAssociatedInterfaceBindersForRenderFrameHost
This deprecates Separate JSSolanaProvider from gin::Wrappable

cc @bridiver