chore(shared): move Glean YAML and generated web code out of fxa-shared
Because: * The FxA Glean YAML already lives in libs/shared/metrics/glean * Only fxa-settings uses the generated Glean web code This commit: * Removes the Glean YAML and pair-reasons.ts from fxa-shared * Moves the generated web code into fxa-settings src/lib/glean/web * Points the glean scripts of auth, content and settings at the registry * Runs glean-lint in the fxa-settings lint script Closes FXA-14711