Tidy up log tests

Bamboo doesn't seem to be causing issues now, so assume
[Fixes #52871199] [bs-176] -Djava.util.logging.config.file
is passed to log4j as a file name?
Ignore exceptions while resolving placeholders in PropertySources

When a PropertySourcesPropertyValues is used to bind Environment
values to a bean (or the SpringApplication) it tries to resolve
placeholders eagerly in the Environment. Any that fail might not
actually be a problem for users (until validation is done it's
impossible to tell even whether that value was needed for the
ongoing binding or not).

Fixed by ignoring exceptions in the PropertySourcesPropertyValues
constructor.

Fixes gh-108
Add support for @GrabExclude to AetherGrapeEngine

@GrabExclude can now be used to exclude certain transitive dependencies.
In Aether (Maven), exclusions are applied to an individual dependency
rather than being global. In Grape, exclusions are global.
AetherGrapeEngine adheres to the Grape convention by applying every
exclusion create by @GrabExclude to every dependency, effectively making
them global.
Add detailed download reporting to AetherGrapeEngine

Groovy's Grape allows a user to enable download reports using the
system property groovy.grape.report.downloads. This commit updates
AetherGrapeEngine to honour this property and produce a detailed
download report when the system property is set to true. In the
absence of the system property, or when it's set to a value other than
true, the existing summary report is still produced.

[bs-344]
[60145094]
Fix CliTester so that sample integration tests can be run
Remove Boot-specifics from AetherGrapeEngine

With the goal of making AetherGrapeEngine generally useful with Groovy,
this commit removes any Boot specifics from it. Specifically, there
is now only a single default repository: Maven Central. The
Boot-specific Spring milestone and snapshot repositories are now added
via @GrabResolver annotations that are added using an ASTTransformation.

As part of this change, AetherGrapeEngine has also been updated to store
its repositories using a LinkedHashSet, this ensures that the same
repository is not used more than once while maintaining their ordering.