refactor(exposition): remove express

[temich]

The next step is the transition to HTTP2.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 38.50416% with 222 lines in your changes are missing coverage. Please review.

Project coverage is 54.09%. Comparing base (a52670a) to head (3f420b7).
Report is 78 commits behind head on dev.

Files	Patch %	Lines
extensions/exposition/source/Gateway.ts	0.00%	29 Missing ⚠️
...sions/exposition/source/directives/octets/Fetch.ts	0.00%	29 Missing ⚠️
...ions/exposition/source/directives/octets/Delete.ts	0.00%	19 Missing ⚠️
...sions/exposition/source/directives/octets/Store.ts	0.00%	18 Missing ⚠️
extensions/exposition/source/HTTP/Context.ts	76.11%	16 Missing ⚠️
...nsions/exposition/source/directives/octets/List.ts	0.00%	14 Missing ⚠️
...ons/exposition/source/directives/octets/Permute.ts	0.00%	12 Missing ⚠️
...nsions/exposition/source/directives/auth/Incept.ts	0.00%	11 Missing ⚠️
extensions/exposition/source/HTTP/messages.ts	70.96%	9 Missing ⚠️
extensions/exposition/source/Mapping.ts	0.00%	7 Missing ⚠️
... and 20 more

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Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #525      +/-   ##
==========================================
- Coverage   56.13%   54.09%   -2.05%     
==========================================
  Files         318      334      +16     
  Lines       10405    11144     +739     
  Branches     1260     1280      +20     
==========================================
+ Hits         5841     6028     +187     
- Misses       4564     5116     +552     

Flag	Coverage Δ
unit	54.09% <38.50%> (-2.05%)	⬇️

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[tinovyatkin]

It's not always a good idea to do 1:1 mapping between searchParams and an object as search params can have repeated queries (for example, to represent an array of value in a standard way).
Are we sure we never will want repeated parameters in the searchParams? I would rather keep query as standard URLSearchParams as it seems to be more flexible.

[temich]

Any operation in Toa accepts Request type. Exposition definitely transforms HTTP Request into operation Request (body goes to input, and query string parsed into query).

There is no such thing as an arbitrary query string in the Exposition. Anything not matching Query type will not pass operation call's validation and result in Bad Request.