(#246) AgileScreen: remove unwanted loading blur; code refactoring

[ryanw-mobile]

This fix removes the duplicated loading blur effect, so it should not be triggered when the screen already has a chart shown during the refresh.

Also consolidates chart data generation functions with unit tests added.

[codacy-production[bot]]

Coverage summary from Codacy

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Coverage variation	Diff coverage
:white_check_mark: -0.15% (target: -1.00%)	:white_check_mark: 1.75%

Coverage variation details

| | Coverable lines | Covered lines | Coverage | | ------------- | ------------- | ------------- | ------------- | | Common ancestor commit (8b848542a13a3fa09643ac0a38e68268552212f5) | 2135 | 1398 | 65.48% | | | Head commit (a97e9a309b297c188cac74251ccaa23456812020) | 2140 (+5) | 1398 (+0) | 65.33% (**-0.15%**) | **Coverage variation** is the difference between the coverage for the head and common ancestor commits of the pull request branch: ` - `

Diff coverage details

| | Coverable lines | Covered lines | Diff coverage | | ------------- | ------------- | ------------- | ------------- | | Pull request (#256) | 114 | 2 | **1.75%** | **Diff coverage** is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: `/ * 100%`

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