Update tests for 'Model' component

[YeluriKetan]

Changes

• Remove unused methods like hashCode()
• Update and increase testing for the model component
• Purge SampleDataUtil and replace its uses with TypicalXXXXLists
• Update self PPP

Issues

• Resolves Increase testing for Model component #228

Preview

• IntelliJ coverage report
  

• Jacoco coverage report
  

Testing

Test application to check for any regressions from removing existing methods.

[codecov-commenter]

Codecov Report

Merging #231 (9774741) into master (d577b66) will increase coverage by 3.15%.
The diff coverage is 95.45%.

@@             Coverage Diff              @@
##             master     #231      +/-   ##
============================================
+ Coverage     71.82%   74.97%   +3.15%     
- Complexity      786      813      +27     
============================================
  Files           122      121       -1     
  Lines          2353     2278      -75     
  Branches        254      250       -4     
============================================
+ Hits           1690     1708      +18     
+ Misses          578      513      -65     
+ Partials         85       57      -28     

Impacted Files	Coverage Δ
src/main/java/seedu/address/model/FriendsList.java	100.00% <ø> (+5.88%)	⬆️
src/main/java/seedu/address/model/GamesList.java	100.00% <ø> (+17.85%)	⬆️
src/main/java/seedu/address/model/Model.java	100.00% <ø> (ø)
...rc/main/java/seedu/address/model/ModelManager.java	100.00% <ø> (+5.26%)	⬆️
...main/java/seedu/address/model/friend/FriendId.java	100.00% <ø> (+20.00%)	⬆️
.../model/friend/FriendIdMatchesKeywordPredicate.java	100.00% <ø> (+14.28%)	⬆️
...in/java/seedu/address/model/friend/FriendName.java	100.00% <ø> (+16.66%)	⬆️
...main/java/seedu/address/model/friend/Schedule.java	87.17% <ø> (+14.67%)	⬆️
.../seedu/address/model/friend/UniqueFriendsList.java	100.00% <ø> (+4.54%)	⬆️
...del/friend/exceptions/InvalidDayTimeException.java	100.00% <ø> (+50.00%)	⬆️
... and 29 more

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[MarcusTXK]

LGTM, nice job with the tests and cleanup of unused code. Tested and all works well.