Update the generate features flow in dev mode to write to a temp generated features file when generating to `target`/`build`

[TrevCraw]

The current generate features flow in dev mode relies on tracking and copying the generated features file in the src dir. Since we want to generate to the server dir only by default, this flow needs to be modified. Unfortunately, we cannot generate directly to the server dir while in the dev mode loop, as it will result in server errors with not being able to find the feature definitions since the features have not been installed yet (refer to https://github.com/OpenLiberty/ci.maven/issues/1526#issuecomment-1136022404). This means we need to keep the current flow of copying the generated features file to the server dir after installing features. The theory is that we should be able to replace the generated file from src with one generated in a temp dir.

The proposal is to write the generated file to a hidden temp dir inside the target/build dir, similar to how we handle the temp containerfile for devc, which is written to the hidden devc dir (refer to the prepareTempContainerfile method in DevUtil - https://github.com/OpenLiberty/ci.common/blob/876db0bb7fe3a6e33ced9b4e75112fc683e9e862/src/main/java/io/openliberty/tools/common/plugins/util/DevUtil.java#L1263)

The first place to start would be to write the generated file to a temp dir. This requires setting up a dev mode specific parameter for the generate features goal/task. Afterwards, it would be prudent to go through the generate features flow in dev mode to check and see if other changes are required (i.e. the copyFile method call in processConfigFileChanges should be updated to pass the "generatedFeaturesFileDir" instead of the configDirectory).

Another thing to consider is whether or not the isGeneratedFeaturesFile checks should always be against the src file location, or be src or temp depending on the value of generateToSrc (i.e. will changes to the temp file be picked up? Assumption is no. What if the src generated file changes while generateToSrc is false? How to react then?).