Improve iOS Text Mapper performance

[louiszawadzki]

What does this PR do?

Improve performance of RN SR.

Motivation

The two calls that were taking the most CPU time were:

• effectiveFont
  • it creates a new font object every time
  • font information is eventually dropped
• UIColor.black.cgColor
  • this calls localized string on every call and makes it a long call
  • we can initialize the color only once

There's a huge drop in CPU ticks per seconds with this on a test view:

• without the change: 299
• without the RN integration (sending all wireframes): 171
• this version (includes sending only wireframes within screen): 139
• no SR: 129

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests
• Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)
• If this PR is auto-generated, please make sure also to manually update the code related to the change

[maxep]

👍

[maxep]

TIL :)