Adventure map, Creature generators, clearly display the number of creatures available in the recruitment request message

[LeHerosInconnu]

I suggest to clearly display the number of creatures available in the recruitment request message.

A few examples:
In fheroes2:

"...wish to join you.
(Available: 18.)

Do you accept?"

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"...for a price.
(Available: 2.)

Do you wish to recruit Dragons?"

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"...as mercenaries.
(Available 5.)

Do you want to recruit any Trolls?"

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"...for a price.
(Available 4.)

Do you want to recruit Liches?"

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Related issue: #1922.