This adds a spotless formatting step using the new pkl formatter.
This only formats Pkl sources in the stdlib, because other sources
are possibly test input and not meant to be formatted.
When we updated spotless's Java and Kotlin formatter, we changed the underlying
formatting rules.
However, due to spotless ratcheting, these formatting changes don't get applied unless a file
gets touched in a commit.
To avoid future PRs introducing lines of change that aren't related to the intention of the PR,
this is a one-time format of all files.
- Fix and clean up the pkl-commons-test build script.
- Change tests to read test packages/certs directly from
the file system instead of packaging and reading them
from the class path.
- Update expected checksums of some test packages.
- Fix a conflict between Pkl's and Gradle's
Kotlin libraries in the pkl-gradle project.
- Fix build deprecation warnings.
- Ensure Gradle distribution integrity with `distributionSha256Sum`.
- Manually verify integrity of Gradle wrapper added by this commit.
