refactor asyncio

[Danstiv]

The logic for checking and executing asynchronous/synchronous functions is moved to the Client.acall method.
I manually tested the following:

1. calling synchronous and asynchronous handlers in the dispatcher works.
2. calling synchronous and asynchronous progress-callbacks in Client.get_file and Client.save_file works.
3. synchronous and asynchronous filters works.

Also, where possible, explicit use of event loop is replaced by function calls in the asyncio module, which is the recommended way and avoids some problems.

[Danstiv]

It looks like it's all working.
Unfortunately, I haven’t found a way to make async to sync work correctly in all cases, namely:

app = pyrogram.Client(...)
@app.message(...)
def sync_handler(client, message):
    message.reply()  # works very poorly / incorrectly / does not work

async def main():
    await app.start()
    await some_blocking_call()
if __name__ == '__main__':
    asyncio.run(main())

A workaround is to add the following calls to the main function:

async def main():
    pyrogram.sync.unwrap()
    pyrogram.sync.wrap()
    await app.start()
    await some_blocking_call()

[Danstiv]

@KurimuzonAkuma

[Danstiv]

I have rebased and manually reread resulting diff. Looks fine.