FED-2979 Clean up dependency ranges, clean out the lint trap

[aaronlademann-wf]

Motivation

1. During the null safety migration, we opened up some rather massive dependency ranges to support both null safe, and non-null safe dependencies.
2. After upgrading these dependencies, and the SDK minimum - we have some new lints we should address.

Now that this lib is null safe, those ranges are inaccurate and unnecessary - and can cause bloated CI times due to slower pub get times.

Changes

1. Bump the Dart SDK Minimum to 2.19.0
2. Bump all package dependency minimums to their minimum null safe version
3. Clean the lint trap