* drop php 7.4 support
update composer.json minimums, and run rector over the code to update what it can. changed some static analysis
config to fix some rector-induced failures.

* adding union typehints

* reformat constructor property promotions

* updating/removing phpdoc

* suppress protobuf extension complaint
submitted a PR upstream to fix phan stubs

* don't validate packages against 7.4

* remove php8 polyfill

* fix readonly comments

* apply trailing commas to multiline fixer
upgrade php-cs-fixer, and apply a new rule for multiline comments

* remove unreachable default match arms for protobuf serializer

* adding more union types to vars

* use weakmap directly

* remove handling for not-supported WeakMap

* spacing

* bump php to 8.1, apply rector
* readonly and typehints
* suppress a dodgy readonly property conversion
* remove some redundant readonly phpdocs
* dont run workflows against 8.0
* more readonly and typehints
* phpdoc reformat
* typehints
* remove php81 polyfill
* revert a rector BC breaking change, and disable that rector for ParentBased

* enable timeout for http transports
Attempt to do our own discovery for some well-known PSR-18 clients, which allows
for configuring timeout (and in future certificates, keys etc).
This is not complete and a prototype for feedback, but I've updated an example to
show that it works for Guzzle and Symfony http clients

* improve client discovery

* refactor, test, add more implementations

* add timeout for logs and metrics

* migrate Clock classes to API
- move Clock* + Util into API
- add a deprecated wrapper for ClockFactory and Util
- remove unused StopWatch* classes

* review feedback

* replace ClockFactory with Clock
It's not really a factory, and really only provides access to a system clock. Create a
Clock class which is more clear in its purpose.

* remove time Util class
per review feedback, it's only used in Zipkin. Removed some unused consts from ClockInterface

* Apply suggestions from code review

Co-authored-by: Tobias Bachert <[email protected]>

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Co-authored-by: Tobias Bachert <[email protected]>

php8.4 deprecates implicit null (now checked by phan)