Deprecate SecretsManager and test new client

[withinboredom]

Description

This deprecates the SecretManager and adds tests for the new client

Issue reference

We strive to have all PR being opened based on an issue, where the problem or feature have been discussed prior to
implementation.

Please reference the issue this PR: #36

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Tests pass
• Created/updated tests
• Extended the documentation

[codecov-commenter]

Codecov Report

Merging #99 (54c88c7) into main (6fb3015) will increase coverage by 1.40%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##               main      #99      +/-   ##
============================================
+ Coverage     66.70%   68.10%   +1.40%     
  Complexity      455      455              
============================================
  Files            59       59              
  Lines          1682     1690       +8     
============================================
+ Hits           1122     1151      +29     
+ Misses          560      539      -21     

Impacted Files	Coverage Δ
src/lib/Client/DaprClient.php	53.84% <ø> (ø)
src/lib/SecretManager.php	75.00% <ø> (ø)
src/lib/Client/HttpSecretsTrait.php	100.00% <100.00%> (+100.00%)	⬆️

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