Ability to find an envelope instance from the given stack

[viktorprogger]

Q	A
Is bugfix?	❌
New feature?	✔️
Breaks BC?	❌

This PR allows to obtain an envelope instance from envelope stack:

$idEnvelope = $message instanceof EnvelopeInterface ? $message->getEnvelopeFromStack(IdEnvelope::class) : IdEnvelope::fromMessage($message);

If the envelope you need uses EnvelopeTrait, it's more simple: code IdEnvelope::getEnvelopeFromMessage($message) will have the same effect as above.

[viktorprogger]

This approach will return an unwanted value in case it is overwritten somewhere in stack by an envelope with another class name. Closing.