Avoid "functions" from dependencies

[GrahamCampbell]

The aim of this PR is to avoid the use of functions provided by our dependencies. This means using their new Utils classes, and bumping their minimum versions (guzzlehttp/promises:^1.4; guzzlehttp/psr7:^1.7). Note that similar changes were already implemented for Guzzle 7.0 itself, but not its dependencies, which we are going to address now, for Guzzle 7.1.

TODO:

• Implement upstream guzzlehttp/promises changes (Extracted functions to static methods promises#113)
• Implement upstream guzzlehttp/psr7 changes (Extracted functions to static methods psr7#345)
• Merge [6.5] Fixed tests #2720 and perform 6.5 -> 7.1 merge
• Update composer.json with ^1.4 and ^1.7
• Replace all uses of functions with their static method replacements
• Update documentation and examples
• Tag guzzlehttp/promises 1.4.0 and remove @dev
• Tag guzzlehttp/psr7 1.7.0 and remove @dev
• Update change log

Mappings:

Original Function	Replacement Method
GuzzleHttp\Promise\queue	GuzzleHttp\Promise\Utils::queue
GuzzleHttp\Promise\task	GuzzleHttp\Promise\Utils::task
GuzzleHttp\Promise\promise_for	GuzzleHttp\Promise\Create::promiseFor
GuzzleHttp\Promise\rejection_for	GuzzleHttp\Promise\Create::rejectionFor
GuzzleHttp\Promise\exception_for	GuzzleHttp\Promise\Create::exceptionFor
GuzzleHttp\Promise\iter_for	GuzzleHttp\Promise\Create::iterFor
GuzzleHttp\Promise\inspect	GuzzleHttp\Promise\Utils::inspect
GuzzleHttp\Promise\inspect_all	GuzzleHttp\Promise\Utils::inspectAll
GuzzleHttp\Promise\unwrap	GuzzleHttp\Promise\Utils::unwrap
GuzzleHttp\Promise\all	GuzzleHttp\Promise\Utils::all
GuzzleHttp\Promise\some	GuzzleHttp\Promise\Utils::some
GuzzleHttp\Promise\any	GuzzleHttp\Promise\Utils::any
GuzzleHttp\Promise\settle	GuzzleHttp\Promise\Utils::settle
GuzzleHttp\Promise\each	GuzzleHttp\Promise\Each::of
GuzzleHttp\Promise\each_limit	GuzzleHttp\Promise\Each::ofLimit
GuzzleHttp\Promise\each_limit_all	GuzzleHttp\Promise\Each::ofLimitAll
!GuzzleHttp\Promise\is_fulfilled	GuzzleHttp\Promise\Is::pending
GuzzleHttp\Promise\is_fulfilled	GuzzleHttp\Promise\Is::fulfilled
GuzzleHttp\Promise\is_rejected	GuzzleHttp\Promise\Is::rejected
GuzzleHttp\Promise\is_settled	GuzzleHttp\Promise\Is::settled
GuzzleHttp\Promise\coroutine	GuzzleHttp\Promise\Coroutine::of
GuzzleHttp\Psr7\str	GuzzleHttp\Psr7\Message::toString
GuzzleHttp\Psr7\uri_for	GuzzleHttp\Psr7\Utils::uriFor
GuzzleHttp\Psr7\stream_for	GuzzleHttp\Psr7\Utils::streamFor
GuzzleHttp\Psr7\parse_header	GuzzleHttp\Psr7\Header::parse
GuzzleHttp\Psr7\normalize_header	GuzzleHttp\Psr7\Header::normalize
GuzzleHttp\Psr7\modify_request	GuzzleHttp\Psr7\Utils::modifyRequest
GuzzleHttp\Psr7\rewind_body	GuzzleHttp\Psr7\Message::rewindBody
GuzzleHttp\Psr7\try_fopen	GuzzleHttp\Psr7\Utils::tryFopen
GuzzleHttp\Psr7\copy_to_string	GuzzleHttp\Psr7\Utils::copyToString
GuzzleHttp\Psr7\copy_to_stream	GuzzleHttp\Psr7\Utils::copyToStream
GuzzleHttp\Psr7\hash	GuzzleHttp\Psr7\Utils::hash
GuzzleHttp\Psr7\readline	GuzzleHttp\Psr7\Utils::readLine
GuzzleHttp\Psr7\parse_request	GuzzleHttp\Psr7\Message::parseRequest
GuzzleHttp\Psr7\parse_response	GuzzleHttp\Psr7\Message::parseResponse
GuzzleHttp\Psr7\parse_query	GuzzleHttp\Psr7\Query::parse
GuzzleHttp\Psr7\build_query	GuzzleHttp\Psr7\Query::build
GuzzleHttp\Psr7\mimetype_from_filename	GuzzleHttp\Psr7\MimeType::fromFilename
GuzzleHttp\Psr7\mimetype_from_extension	GuzzleHttp\Psr7\MimeType::fromExtension
GuzzleHttp\Psr7\_parse_message	GuzzleHttp\Psr7\Message::parseMessage
GuzzleHttp\Psr7\_parse_request_uri	GuzzleHttp\Psr7\Message::parseRequestUri
GuzzleHttp\Psr7\get_message_body_summary	GuzzleHttp\Psr7\Message::bodySummary
GuzzleHttp\Psr7\_caseless_remove	GuzzleHttp\Psr7\Utils::caselessRemove

---

Closes #2740.

[Nyholm]

All these changes looks good.

Thank you.

[Nyholm]

The Promises package and the PSR7 package is now tagged.

[Nyholm]

Awesome work.

Thank you