Remove setting copy settings on resize to false

[jasontedor]

As the copy_settings REST parameter and copySettings transport field was deprecated in 6.4.0 slated for removal in 8.0.0, this commit puts us farther down that path by:

• defaulting copy settings to true
• preventing settings copy settings to false

Relates #28347, relates #30255

[colings86]

@jasontedor This process for removal is a little different than I envisaged. I had thought that we would:

• Add copySettings in 6.4.0 defaulted to false and add a deprecation warning if copySettings was not provided stating that the behaviour will change in 7.0. the actual copySettings parameter would not be deprecated though since we want people to use it in 6.4-6.last
• In 7.0, change the default of copySettings to true, and make it so we emit deprecation warnings if the parameter is explicitly set on a resize request explaining that the parameter will be removed in 8.0. We wouldn't restrict which values of copySettings can be used in 7.0 though, just emit the warning if it is used.
• In 8.0, remove the copySettings parameter completely

The worry I have with the approach in this PR is that it puts the hard break in 7.0 since there is no way of not copying settings so to me it seems that its the same as just removing the parameter in 7.0?

[jasontedor]

@colings86 I am following the plan that we outlined here: #28347

I am fine with changing the plan, but I think the place for that discussion is the source issue.

[colings86]

@jasontedor I left a comment on #28347 with my comments from above so we can discuss. Sorry I didn't think about this and bring up the concern earlier

[elasticmachine]

Pinging @elastic/es-core-infra

[jasontedor]

Superseded by #30404