Wholesale cleanup of all history plugins

- remove the use of redundant cite
- minor cleanups to history.plugin.bash
- set explicit load orders for history-search and history-substring-search
- add new plugin history-eternal
- replace superfluous trap for managing HISTTIMEFORMAT changes

plugins/available/history-eternal.plugin.bash

@@ -0,0 +1,20 @@
+# shellcheck shell=bash
+about-plugin 'eternal bash history'
+
+# Load after the history plugin
+# BASH_IT_LOAD_PRIORITY: 375
+
+# Modify history sizes before changing location to avoid unintentionally
+# truncating the history file early.
+
+# "Numeric values less than zero result in every command being saved on the history list (there is no limit)"
+export HISTSIZE=-1
+
+# "Non-numeric values and numeric values less than zero inhibit truncation"
+export HISTFILESIZE='unlimited'
+
+# Use a custom history file location so history is not truncated
+# if the environment ever loses this "eternal" configuration.
+HISTDIR="${XDG_STATE_HOME:-${HOME?}/.local/state}/bash"
+[[ -d ${HISTDIR?} ]] || mkdir -p "${HISTDIR?}"
+export HISTFILE="${HISTDIR?}/history"