Avoid compiling regexes in ObjectJsonStreamer

[lemnik]

Goal

Reduce the overhead of constructing ObjectJsonStreamer instances (and therefore leaving complex breadcrumbs) by sharing the default redactedKeys (which is immutable).

Design

An ObjectJsonStreamer is allocated internally each time a breadcrumb metadata item needs to be JSON encoded early (because it is too complex for the NDK layer to handle directly). Each of these was causing the default redactedKeys pattern to be compiled. Since the default redactedKeys set is immutable, it can be safely shared instead.

Testing

Relied on existing tests.

[bugsnagbot]

Android notifier sizes

Format	Size impact of Bugsnag (kB)	Size impact of Bugsnag when Minified (kB)
APK	1843.96	1668.06
arm64_v8a	626.95	450.82
armeabi_v7a	561.42	385.29
x86	700.66	524.53
x86_64	671.99	495.86

Generated by 🚫 Danger

[YYChen01988]

LGTM