http: escape encoded params before sending request

Closes #7931

@TarantoolBot document
Title: Document a percent-encoding of params passed to http client

The HTTP client has `params` option, where a user may provide a table of
query parameters (added in #6832). Those parameters are encoded into a
`?foo=bar&tweedledoo=tweedledee` string verbatim. If a name or a value of
a query parameter contains `&`, `=` (or any another symbol with specific
meaning in the URI query component), the query may be interpreted
incorrectly by a server. Now key and values passed in a table as
`params` option are percent-encoded and then encoded to a query string.
This will be made automatically. Percent-encoding depends on used HTTP
method: with `GET`, `HEAD` and `DELETE` parameters `uri.QUERY_PART`
are used and with other HTTP method `uri.FORM_URLENCODED` is used.