fix: Arango plugin: change default db name to _system

[reachtokish]

Description

ArangoDB has changed it's default db name from default to _system. This PR make the corresponding changes.

Fixes #15899

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

I ran corresponding plugin test cases and passed all test cases.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

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Name	Status	Preview	Updated
appsmith	✅ Ready (Inspect)	Visit Preview	Aug 22, 2022 at 3:26PM (UTC)

[github-actions]

This PR has not seen activitiy for a while. It will be closed in 7 days unless further activity is detected.

[github-actions]

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[sumitsum]

/ok-to-test sha=7814f0f

[github-actions]

Tests running at: https://github.com/appsmithorg/appsmith/actions/runs/3097430363.
Workflow: Appsmith External Integration Test Workflow.
Commit: 7814f0f.
PR: 16198.

[github-actions]

UI Performance test run logs and artifacts: https://github.com/appsmithorg/appsmith/actions/runs/3097430363.
Commit: ``.
Results:

Click to view performance test results

| | Run 1 _^(ms)| Run 2 _^(ms)| Run 3 _^(ms)| Run 4 _^(ms)| Run 5 _^(ms)| Minimum _^(ms)| Median _^(ms)| Mean _^(ms)| Range _^(%) | SD.Sample _^(%) | SD.Population _^(%)|
| ------------- | ------------- | ------------- | ------------- | ------------- | ------------- | ------------- | ------------- | ------------- | ------------- | ------------- |
SELECT_CATEGORY| | | | | | | | | | |
| scripting | 512.24 | 427.83 | 431.99 | 427.81 | 394.33 | 394.33| 427.83| 438.84 | 26.87| 9.97 | 8.92|
| painting | 5.56 | 4.49 | 4.66 | 8.16 | 3.79 | 3.79| 4.66| 5.33 | 81.99| 31.89 | 28.52|
| rendering | 127.54 | 134.52 | 114.15 | 121.96 | 114.08 | 114.08| 121.96| 122.45 | 16.69| 7.19 | 6.44|
BIND_TABLE_DATA| | | | | | | | | | |
| scripting | 1368.25 | 1068.09 | 1222.18 | 1839.31 | 1134.91 | 1068.09| 1222.18| 1326.55 | 58.14| 23.21 | 20.76|
| painting | 33.47 | 19.65 | 25.96 | 28.36 | 17.46 | 17.46| 25.96| 24.98 | 64.09| 26.06 | 23.30|
| rendering | 1061.77 | 879.12 | 934.32 | 665.11 | 946.39 | 665.11| 934.32| 897.34 | 44.20| 16.25 | 14.54|
CLICK_ON_TABLE_ROW| | | | | | | | | | |
| scripting | 1203.82 | 960 | 1036.24 | 1097.19 | 979.6 | 960| 1036.24| 1055.37 | 23.10| 9.36 | 8.37|
| painting | 26.73 | 9.28 | 11.46 | 11.55 | 11.21 | 9.28| 11.46| 14.05 | 124.20| 50.89 | 45.55|
| rendering | 385.42 | 322.21 | 320.99 | 350.25 | 318.04 | 318.04| 322.21| 339.38 | 19.85| 8.50 | 7.60|
UPDATE_POST_TITLE| | | | | | | | | | |
| scripting | 2235.16 | 1768.64 | 1863.16 | 2091.78 | 1483.74 | 1483.74| 1863.16| 1888.5 | 39.79| 15.45 | 13.82|
| painting | 25.36 | 20.11 | 22.41 | 20.86 | 15.15 | 15.15| 20.86| 20.78 | 49.13| 17.95 | 16.07|
| rendering | 574.45 | 544.96 | 537.24 | 583.65 | 516.71 | 516.71| 544.96| 551.4 | 12.14| 4.98 | 4.45|
OPEN_MODAL| | | | | | | | | | |
| scripting | 611.44 | 493.5 | 512.85 | 562.6 | 489.07 | 489.07| 512.85| 533.89 | 22.92| 9.79 | 8.75|
| painting | 25.42 | 19.23 | 10.12 | 12.65 | 13.3 | 10.12| 13.3| 16.14 | 94.80| 38.23 | 34.20|
| rendering | 481.04 | 413.94 | 417.77 | 444.66 | 420.87 | 413.94| 420.87| 435.66 | 15.40| 6.44 | 5.76|
CLOSE_MODAL| | | | | | | | | | |
| scripting | 262.54 | 199.53 | 242.18 | 294.02 | 193.99 | 193.99| 242.18| 238.45 | 41.95| 17.76 | 15.89|
| painting | 7.86 | 4.88 | 13.06 | 18.17 | 12.42 | 4.88| 12.42| 11.28 | 117.82| 45.30 | 40.51|
| rendering | 410.12 | 389.94 | 414.63 | 385.21 | 373.79 | 373.79| 389.94| 394.74 | 10.35| 4.36 | 3.90|
SELECT_WIDGET_MENU_OPEN| | | | | | | | | | |
| scripting | 1130.84 | 1055.65 | 1170.14 | 1063.65 | 986.71 | 986.71| 1063.65| 1081.4 | 16.96| 6.58 | 5.89|
| painting | 7.19 | 14.6 | 8.19 | 12.89 | 5.51 | 5.51| 8.19| 9.68 | 93.90| 40.08 | 35.85|
| rendering | 704.69 | 661.96 | 765.87 | 677.83 | 613.57 | 613.57| 677.83| 684.78 | 22.24| 8.20 | 7.33|
SELECT_WIDGET_SELECT_OPTION| | | | | | | | | | |
| scripting | 203.9 | 167.95 | 201.83 | 177.37 | 164.32 | 164.32| 177.37| 183.07 | 21.62| 10.21 | 9.13|
| painting | 4.11 | 6.7 | 3.17 | 3.92 | 2.97 | 2.97| 3.92| 4.17 | 89.45| 35.73 | 31.89|
| rendering | 336.37 | 333.26 | 355.57 | 341.94 | 318.86 | 318.86| 336.37| 337.2 | 10.89| 3.96 | 3.54|