[fix][common] Resolve ControlConfig linkage and restore CI

[ketor]

Runtime fix

• resolve every production boolean ControlConfig flag by registered gflags name, removing the direct reference to the internal braft symbol that broke static linking
• run registered validators consistently and preserve the Dingo warning for every dangerous raft-meta enable request
• report missing flags, invalid values, and validator rejection through the per-variable response
• make the BR client treat per-variable errors as node failures instead of reporting false success

CI fix

• use the Ubuntu dingo-eureka dependency image and pin DINGO_EUREKA_INSTALL_PATH explicitly
• install the Rust 1.78 toolchain required by tantivy
• compile unit tests and run the ControlConfig regression suites in Ubuntu CI
• align the Docker build guide with the dependency image used by CI

Review remediation

• split runtime and CI changes into separate commits with explanatory bodies
• replace duplicate bool handlers with HandleBoolControlConfigVariableByName
• add direct tests for unknown flags, invalid values, already-set values, numeric bools, validator rejection, and braft flag registration
• guard fixture restoration after failed registration setup

Fixes the failures in runs 33480985469 and 33480985453.

[yuhaijun999]

LGTM