Remove panic method in crdt text

[emplam27]

Remove panic method in crdt text

• go sdk crdt text has the condition that cause panic
• remove panic prevent shutdown server when crdt text error occurred

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #501

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Additional documentation:

Checklist:

• Added relevant tests or not required
• Didn't break anything

[codecov]

Codecov Report

Merging #522 (adb262c) into main (969e509) will decrease coverage by 0.78%.
The diff coverage is 37.61%.

❗ Current head adb262c differs from pull request most recent head 350a5cd. Consider uploading reports for the commit 350a5cd to get more accurate results

@@            Coverage Diff             @@
##             main     #522      +/-   ##
==========================================
- Coverage   50.61%   49.84%   -0.78%     
==========================================
  Files          64       64              
  Lines        5751     5860     +109     
==========================================
+ Hits         2911     2921      +10     
- Misses       2471     2534      +63     
- Partials      369      405      +36     

Impacted Files	Coverage Δ
pkg/document/crdt/array.go	34.04% <0.00%> (-2.33%)	⬇️
pkg/document/crdt/counter.go	53.08% <0.00%> (ø)
pkg/document/crdt/object.go	21.62% <0.00%> (-1.91%)	⬇️
pkg/document/internal_document.go	21.31% <0.00%> (-0.73%)	⬇️
pkg/document/crdt/root.go	73.33% <25.00%> (-6.67%)	⬇️
pkg/document/crdt/text.go	54.05% <29.16%> (-6.16%)	⬇️
api/converter/from_bytes.go	62.35% <30.00%> (-2.29%)	⬇️
pkg/document/document.go	45.23% <30.00%> (-6.88%)	⬇️
pkg/llrb/llrb.go	69.87% <43.63%> (-10.45%)	⬇️
pkg/document/crdt/rga_tree_split.go	65.05% <45.94%> (-8.45%)	⬇️
... and 2 more

[hackerwins]

@emplam27 Thanks for your contribution.

crdt.Text uses RGATreeSplit and SplayTree. So To remove all panic from crdt.Text, we also need to remove panic in RGATreeSplit and SplayTree.

### pkg/document/crdt/rga_tree_split.go

46:// argument is nil, it would panic at runtime.
49:		panic("RGATreeSplitNodeID cannot be null")
351:		panic("the node of the given id should be found: " + s.StructureAsString())
367:		panic("offset should be less than or equal to length: " + s.StructureAsString())

### pkg/splay/splay.go
206:		panic(fmt.Sprintf(

https://github.com/yorkie-team/yorkie/blob/main/design/data-structure.md#overview

But since SplayTree is also used in Array, I think it would be better to remove it from another PR(e.g. Remove panic in crdt.Array).

[emplam27]

@hackerwins
i'm done to remove rga_tree_split's panic.
then, how about element_rht and rga_tree_list's panic? is it ok to remove those panics?

### pkg/document/crdt/element_rht.go
173:		panic("fail to find: " + elem.CreatedAt().Key())

### pkg/document/crdt/rga_tree_list.go
209:		panic("fail to find the given createdAt: " + createdAt.Key())
241:		panic("fail to find the given prevCreatedAt: " + prevCreatedAt.Key())
246:		panic("fail to find the given createdAt: " + createdAt.Key())
261:		panic("fail to find the given prevCreatedAt: " + createdAt.Key())
278:		panic("fail to find the given createdAt: " + elem.CreatedAt().Key())
290:		panic("fail to find the given createdAt: " + createdAt.Key())

[hackerwins]

Thanks for your contribution. 👍