feat: modernization part 2

[feywind]

This is a follow-up for these two PRs:

https://github.com/googleapis/nodejs-bigtable/pull/1739 https://github.com/googleapis/nodejs-bigtable/pull/1740

This takes care of some missing pieces that were discovered by further discussion:

• GcRuleBuilder is a more TypeScript-heavy way to validate ModifyColumnFamilies garbage collection rules, with type checking taking care of a lot of the constraints, and some minimal runtime checking for JavaScript users.
• Rather than raw GAPIC, the focus has shifted to selective GAPIC subclasses that can augment them. This is specifically done to assist with RestoreTable and waiting for table consistency.
• Data plane samples have been removed, as we don't want to encourage users to use them.
• Generated samples and tests have been auto-edited to use the selective GAPIC classes.
• Manual sample snippets have been updated to reflect the expected admin access and GcRuleBuilder usage.

There is still a CI issue that will need to be corrected before this can be merged. I don't think it's the result of this change, but I also don't want to chance it.