feature: add minimum breadcrumb level filtering

[KishanPRao]

Summary

Adds a way to set the global minimum breadcrumb level while enabling breadcrumbs, which allows filtering the breadcrumbs from being added, when below the minimum level.

Changes

• Breadcrumbs.java: 4 new enableBreadcrumbs backward-compatible overloads with minBreadcrumbLevel argument, plus getMinBreadcrumbLevel().
• BacktraceBreadcrumbs.java: stores the minBreadcrumbLevel threshold, default DEBUG level, drops below-threshold breadcrumbs during addBreadcrumb, logs the level in the configuration breadcrumb.
• BacktraceBase.java: forwards the new overloads and getter to the breadcrumb implementation.
• BacktraceBreadcrumbsTest.java: 5 tests covering below/at/above threshold, default level, re-enable update level, new breadcrumb.level attribute in config.
• MainActivity.java: example app sets min level to INFO and emits one breadcrumb per level in sendReport to showcase the filter.
• BreadcrumbsReader.java: included JSON-parse check with existing substring timestamp match; issue exposed by the new breadcrumb.level attribute shifting QueueFile byte alignment.

ref: BT-6699

[melekr]

lgtm 🚀