boblight: reduce cpu time spent on memcopy and parsing rgb values

[The-Master777]

The amount of memory allocations in BoblightClientConnection is reduced drastically.

BoblightClientConnection used to perform a huge amount of memcopy-operations - mostly involving read only string data – that led to high CPU usage. Now QStringRef is used to store tokenized Boblight messages instead of creating read-only copies of such strings.

The parsing of RGB values (given as float-strings) is optimized to be allocation-free. This is archived using a native (thus performant) implementation based on QChar character values and mostly int-arithmetic.

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Docs
• Build-related changes
• Other, please describe:

If changing the UI of web configuration, please provide the before/after screenshot:

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing setups:

The PR fulfills these requirements:

• When resolving a specific issue, it's referenced in the PR's body (e.g. Fixes: #xxx[,#xxx], where "xxx" is the issue number)

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature
• Related documents have been updated (docs/docs/en)
• Related tests have been updated

PLEASE DON'T FORGET TO ADD YOUR CHANGES TO CHANGELOG.MD

• Yes, CHANGELOG.md is also updated

To avoid wasting your time, it's best to open a feature request issue first and wait for approval before working on it.

Other information:

Benchmarks show the number of CPU-Cycles consumed by memory allocation and parsing plummet significantly freeing valuable system resources. Measured on raspberry pi 4 with perf on debian AArch64, 10 seconds of real life boblight data, 600 LEDs.

Performance with refactoring:

  Children      Self  Command         Shared Ob  Symbol
+   29.78%     0.50%  HyperionThread  hyperiond  [.] BoblightClientConnection::readData      
-   16.29%     1.62%  HyperionThread  hyperiond  [.] BoblightClientConnection::handleMessage 
   - 14.67% BoblightClientConnection::handleMessage                                          
      + 6.92% QString::splitRef                                                              
      + 3.08% Hyperion::setInput                                                             
      + 1.27% BoblightClientConnection::parseByte                                            
        0.98% QString::compare_helper                                                        
        0.58% QStringRef::operator==                                                         
   + 1.62% thread_start                                                                      
+    1.32%     0.14%  HyperionThread  hyperiond  [.] BoblightClientConnection::parseByte     
+    1.20%     1.18%  HyperionThread  hyperiond  [.] BoblightClientConnection::parseFloat    
+    0.73%     0.11%  HyperionThread  hyperiond  [.] BoblightClientConnection::readMessage   
     0.25%     0.25%  HyperionThread  hyperiond  [.] BoblightClientConnection::parseUInt     

Performance baseline:

  Children      Self  Command         Shared Ob  Symbol
-   50.92%     0.95%  HyperionThread  hyperiond  [.] BoblightClientConnection::readData      
   - 49.97% BoblightClientConnection::readData                                               
      + 36.55% BoblightClientConnection::handleMessage                                       
      + 9.93% QByteArray::mid                                                                
        0.76% _int_free                                                                      
        0.76% QString::fromLatin1_helper                                                     
   + 0.95% thread_start                                                                      
-   36.55%     0.98%  HyperionThread  hyperiond  [.] BoblightClientConnection::handleMessage 
   - 35.57% BoblightClientConnection::handleMessage                                          
      + 11.61% QString::split                                                                
      + 10.78% QString::toFloat                                                              
      + 2.89% QList<QString>::~QList                                                         
      + 2.23% Hyperion::setInput                                                             
      + 1.60% QString::fromAscii_helper                                                      
      + 1.57% QString::toUInt                                                                
        0.78% QString::compare_helper                                                        
        0.74% _int_free                                                                      ```

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[Paulchen-Panther]

qmax and qmin would be qt alternatives?

[The-Master777]

Given the Qt documentation using qMax/qMin should be applicable aswell.
When using Qt methods, probably qBound is the out-of-box solution to go for to clamp the values to 0 .. 255 range.

Edit: Addressed this in e60e7f3

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[Paulchen-Panther]

Thank you for your help to Hyperion.