feat(ec2): support not materialize meta data item in cfg

[jinkkkang]

Proposed Commit Message

feat(ec2): configure meta data item in cfg to not materialize

Cloud vendors provide a lot of information in meta data,but some of the
information may not be needed by cloudinit. When iterating through the 
materialization function (helpers/ec2.py), it may need to be ignored,
such as security-credentials in the previous code. We would like to
provide a configuration item to configure the allowable field name to
be ignored. This can save cloudinit startup time when there is a large
amount of data that can be ignored. One case is that in the meta data
provided by Alibaba Cloud, there is a disks item that contains
information about the disks on the instance, but cloudinit does not use
it. When there are a large number of disks in the metadata data, this
can cause many unnecessary HTTP access. This feature allows users to 
ignore accessing some unused data

Additional Context

Test Steps

Merge type

• Squash merge using "Proposed Commit Message"
• Rebase and merge unique commits. Requires commit messages per-commit each referencing the pull request number (#<PR_NUM>)

[jinkkkang]

@TheRealFalcon pls help a review