[Fleet Console] Refactor MRT table configurations and decouple field configs

This change looks big, but it's mostly reformatting and moving stuff around.

Demo: https://20345-a7f37a7-zhangti-mrt-base-infrastructure-dot-luci-milo-dev.appspot.com/ui/fleet/p/chromeos/devices?filters=

Testing Instructions:

* Go to each data table that has column configuration (device table, repairs tables, RRI)
* Verify that the table renders correctly and all cells compute expected data without freezes or failures.
* try customizing columns.

Key changes:

* Co-location of Configs: Moved domain-specific field overrides (accessors and custom renderers) out of table layout files and into feature-specific directories (e.g., chromeos_fields.tsx) to keep overlap high and reduce context switching.
* Generator Standardization: Converted the fixed Repairs table columns to use the dynamic generator pattern we use for other dynamic tables.
* Safety & Security: Enforced rel="noopener noreferrer" on external links and wrapped generated proto enum converters in a try-catch trap to protect against runtime crashes.
* Documentation: Captured the decisions and file organization rules in the official mrt-table-architecture.md record.

Bug: b/479452001
Change-Id: Id4ce8c611fa6aeaba6ae1d23c7a04461e053253c
Reviewed-on: https://chromium-review.googlesource.com/c/infra/luci/luci-go/+/7791645
Commit-Queue: Tiffany Zhang <zhangtiff@chromium.org>
Reviewed-by: Phoebe Tang <phoebetang@google.com>