Docs: some review on stage1-implementors-guide.md
Docs: some review on stage1-implementors-guide.md

This patch :
- Remove duplicate words
- Keep the format of "Entrypoints(run,enter,gc,stop)" consistent
- Fix typo

Signed-off-by: Hu Keping <ce660952c949ad2751377b45317337be332e80ac@huawei.com>

yifan-gu/rocket,sstabellini/rkt,jonboulle/rkt,lucasallan/rkt,jakon89/rkt,intelsdi-x/rkt,coreos/rkt,kinvolk/rkt,shobhit85/rkt,intelsdi-x/rkt,jakon89/rkt,alban/rkt,Wilybald/rkt,sstabellini/rkt,joshix/rkt,rkt/rkt,Shashwatsh/rkt,Wilybald/rkt,shobhit85/rkt,alban/rkt,euank/rkt,achanda/rkt,lucasallan/rkt,jonboulle/rkt,dgonyeo/rkt,cab105/rkt,ybubnov/rkt,rkt/rkt,s-urbaniak/rkt,cab105/rkt,squeed/rkt,dgonyeo/rkt,achanda/rkt,achanda/rkt,dgonyeo/rkt,yifan-gu/rkt,euank/rkt,ybubnov/rkt,squeed/rkt,euank/rkt,Wilybald/rkt,jakon89/rkt,intelsdi-x/rkt,Wilybald/rkt,coreos/rkt,kinvolk/rkt,sstabellini/rkt,alban/rkt,joshix/rkt,kinvolk/rkt,nhlfr/rkt,ybubnov/rkt,nhlfr/rkt,lucasallan/rkt,rkt/rkt,joshix/rkt,Shashwatsh/rkt,yifan-gu/rkt,yifan-gu/rocket,s-urbaniak/rkt,s-urbaniak/rkt,yifan-gu/rocket,shobhit85/rkt,squeed/rkt,joshix/rkt,rkt/rkt,yifan-gu/rkt,lucasallan/rkt,kinvolk/rkt,coreos/rkt,cab105/rkt,nhlfr/rkt,jonboulle/rkt,Shashwatsh/rkt