Remove deprecated CLI flags and references for v8.0.0 (#8142)

Closes #8131

- [x] Remove deprecated flags from beacon_node/src/cli.rs:
- [x] eth1-purge-cache
- [x] eth1-blocks-per-log-query
- [x] eth1-cache-follow-distance
- [x] disable-deposit-contract-sync
- [x] light-client-server
- [x] Remove deprecated flags from lighthouse/src/main.rs:
- [x] logfile
- [x] terminal-total-difficulty-override
- [x] terminal-block-hash-override
- [x] terminal-block-hash-epoch-override
- [x] safe-slots-to-import-optimistically
- [x] Remove references to deprecated flags in config.rs files
- [x] Remove warning messages for deprecated flags in main.rs
- [x] Update/remove related tests in beacon_node.rs


  


Co-Authored-By: Jimmy Chen <jchen.tc@gmail.com>

Co-Authored-By: Jimmy Chen <jimmy@sigmaprime.io>

book/src/help_bn.md

@@ -513,8 +513,6 @@ Flags:
           subscriptions. This will only import attestations from
           already-subscribed subnets, use with --subscribe-all-subnets to ensure
           all attestations are received for import.
-      --light-client-server
-          DEPRECATED
       --log-color [<log-color>]
           Enables/Disables colors for logs in terminal. Set it to false to
           disable colors. [default: true] [possible values: true, false]