Because:
- The session-token Redis main thread runs near saturation and stalls
auth-server requests.
- Each lastAccessTime touch decodes and rewrites the account's whole
session blob in Lua.
This commit:
- Throttles lastAccessTime-only touches per token with a SET NX EX marker key.
- Adds lastAccessTimeUpdates.minIntervalSeconds (default 60, 0 disables).
- Reads session tokens with a plain GET and unpacks them in Node.
- Removes the getSessionTokens_1 Lua script.
- Adds getSessionTokens unpack and error counters.
Closes #FXA-14880