Embed assets in elf file (#2466)

* FBT: file_assets generator
* Elf file: process manifest section externally
* FBT, file_assets generator: add assets signature
* Storage: assets path alias
* Flipper application: assets unpacker
* Apps, Storage: use '/data' alias for apps data
* Storage: copy file to file
* Assets: log flag, fixes
* Update f18 api
* Assets: asserts
* Assets: fix signature_data check
* App assets: example
* Example assets: fix folder structure in readme
* Assets: fix error handling
* Assets builder: use ansii instead of utf-8, use .fapassets section instead of .fapfiles, add assets path to signature
* Elf file: comment strange places
* Storage: totaly optimized storage_file_copy_to_file

applications/examples/example_apps_assets/files/poems/a jelly-fish.txt

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+A Jelly-Fish by Marianne Moore
+
+Visible, invisible,
+A fluctuating charm,
+An amber-colored amethyst
+Inhabits it; your arm
+Approaches, and
+It opens and
+It closes;
+You have meant
+To catch it,
+And it shrivels;
+You abandon
+Your intent—
+It opens, and it
+Closes and you
+Reach for it—
+The blue
+Surrounding it
+Grows cloudy, and
+It floats away
+From you.
+
+source: "https://poets.org/anthology/poems-your-poetry-project-public-domain"

applications/examples/example_apps_assets/files/poems/my shadow.txt

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+My Shadow by Robert Louis Stevenson
+
+I have a little shadow that goes in and out with me,
+And what can be the use of him is more than I can see.
+He is very, very like me from the heels up to the head;
+And I see him jump before me, when I jump into my bed.
+
+The funniest thing about him is the way he likes to grow—
+Not at all like proper children, which is always very slow;
+For he sometimes shoots up taller like an India-rubber ball,
+And he sometimes gets so little that there’s none of him at all.
+
+He hasn’t got a notion of how children ought to play,
+And can only make a fool of me in every sort of way.
+He stays so close beside me, he’s a coward you can see;
+I’d think shame to stick to nursie as that shadow sticks to me!
+
+One morning, very early, before the sun was up,
+I rose and found the shining dew on every buttercup;
+But my lazy little shadow, like an arrant sleepy-head,
+Had stayed at home behind me and was fast asleep in bed.
+
+source: "https://poets.org/anthology/poems-your-poetry-project-public-domain"

applications/examples/example_apps_assets/files/poems/theme in yellow.txt

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+Theme in Yellow by Carl Sandburg
+
+I spot the hills 
+With yellow balls in autumn. 
+I light the prairie cornfields 
+Orange and tawny gold clusters 
+And I am called pumpkins. 
+On the last of October 
+When dusk is fallen 
+Children join hands 
+And circle round me 
+Singing ghost songs 
+And love to the harvest moon; 
+I am a jack-o'-lantern 
+With terrible teeth 
+And the children know 
+I am fooling.
+
+source: "https://poets.org/anthology/poems-your-poetry-project-public-domain"

applications/examples/example_apps_assets/files/test_asset.txt

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+## This is test file content