add a clear method to delete saved data in storage

[dsainati1]

Closes #1245

Adds a new method to the AuthAccount object:

fun clear(_ path: Path): Bool

This function deletes whatever is present at the specified path, destroying any resources, and returns whether anything was present originally.

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• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• Code follows the standards mentioned here
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[codecov-commenter]

Codecov Report

Merging #1253 (2ee3fb9) into master (81c63bf) will increase coverage by 0.01%.
The diff coverage is 94.59%.

@@            Coverage Diff             @@
##           master    #1253      +/-   ##
==========================================
+ Coverage   77.60%   77.61%   +0.01%     
==========================================
  Files         274      274              
  Lines       35233    35261      +28     
==========================================
+ Hits        27341    27369      +28     
  Misses       6805     6805              
  Partials     1087     1087              

Flag	Coverage Δ
unittests	77.61% <94.59%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
runtime/interpreter/interpreter.go	89.19% <89.47%> (+0.06%)	⬆️
runtime/interpreter/account.go	93.16% <100.00%> (+0.17%)	⬆️
runtime/sema/authaccount_type.go	100.00% <100.00%> (ø)

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[github-actions]

Cadence Benchstat comparison

This branch with compared with the base branch onflow:master commit 81c63bf
The command go test ./... -run=XXX -bench=. -shuffle=on -count N was used.
Bench tests were run a total of 7 times on each branch.

Results

	old.txt	new.txt
	time/op		delta
QualifiedIdentifierCreation/One_level-2	3.17ns ± 4%	3.30ns ± 2%	+4.14%	(p=0.008 n=7+6)
ParseArray-2	22.6ms ± 1%	23.1ms ± 2%	+1.88%	(p=0.005 n=6+7)
RuntimeStorageWriteCached-2	169µs ±43%	143µs ± 2%	~	(p=0.731 n=7+6)
RuntimeResourceDictionaryValues-2	16.7ms ± 3%	16.4ms ± 3%	~	(p=0.534 n=7+6)
RuntimeFungibleTokenTransfer-2	1.24ms ± 4%	1.24ms ± 3%	~	(p=0.445 n=7+6)
ParseFungibleToken-2	469µs ± 2%	475µs ± 2%	~	(p=0.165 n=7+7)
ParseInfix-2	24.6µs ± 2%	24.9µs ± 4%	~	(p=0.456 n=7+7)
ParseDeploy/decode_hex-2	1.44ms ± 4%	1.43ms ± 3%	~	(p=1.000 n=7+7)
QualifiedIdentifierCreation/Three_levels-2	161ns ± 2%	163ns ± 4%	~	(p=0.386 n=6+7)
CheckContractInterfaceFungibleTokenConformance-2	168µs ± 3%	171µs ± 5%	~	(p=0.128 n=7+7)
ContractInterfaceFungibleToken-2	47.4µs ± 1%	47.8µs ± 2%	~	(p=0.318 n=7+7)
InterpretRecursionFib-2	2.71ms ± 3%	2.68ms ± 3%	~	(p=0.945 n=7+6)
NewInterpreter/new_interpreter-2	1.16µs ± 5%	1.16µs ± 2%	~	(p=0.781 n=7+7)
NewInterpreter/new_sub-interpreter-2	2.11µs ± 3%	2.10µs ± 3%	~	(p=0.779 n=7+7)
ParseDeploy/byte_array-2	35.0ms ± 3%	34.3ms ± 2%	−2.15%	(p=0.038 n=7+7)
	alloc/op		delta
RuntimeFungibleTokenTransfer-2	233kB ± 0%	234kB ± 0%	+0.40%	(p=0.001 n=7+7)
RuntimeResourceDictionaryValues-2	4.34MB ± 0%	4.34MB ± 0%	+0.02%	(p=0.001 n=7+7)
RuntimeStorageWriteCached-2	83.7kB ± 0%	83.7kB ± 0%	~	(p=0.294 n=6+7)
QualifiedIdentifierCreation/One_level-2	0.00B	0.00B	~	(all equal)
QualifiedIdentifierCreation/Three_levels-2	64.0B ± 0%	64.0B ± 0%	~	(all equal)
CheckContractInterfaceFungibleTokenConformance-2	66.4kB ± 0%	66.4kB ± 0%	~	(p=1.000 n=7+7)
ContractInterfaceFungibleToken-2	26.7kB ± 0%	26.7kB ± 0%	~	(all equal)
InterpretRecursionFib-2	1.21MB ± 0%	1.21MB ± 0%	~	(p=0.385 n=7+6)
NewInterpreter/new_interpreter-2	680B ± 0%	680B ± 0%	~	(all equal)
NewInterpreter/new_sub-interpreter-2	1.06kB ± 0%	1.06kB ± 0%	~	(all equal)
	allocs/op		delta
RuntimeFungibleTokenTransfer-2	4.42k ± 0%	4.43k ± 0%	+0.06%	(p=0.001 n=6+7)
RuntimeResourceDictionaryValues-2	108k ± 0%	108k ± 0%	+0.00%	(p=0.005 n=7+7)
RuntimeStorageWriteCached-2	1.42k ± 0%	1.42k ± 0%	~	(all equal)
QualifiedIdentifierCreation/One_level-2	0.00	0.00	~	(all equal)
QualifiedIdentifierCreation/Three_levels-2	2.00 ± 0%	2.00 ± 0%	~	(all equal)
CheckContractInterfaceFungibleTokenConformance-2	1.07k ± 0%	1.07k ± 0%	~	(all equal)
ContractInterfaceFungibleToken-2	458 ± 0%	458 ± 0%	~	(all equal)
InterpretRecursionFib-2	25.0k ± 0%	25.0k ± 0%	~	(all equal)
NewInterpreter/new_interpreter-2	11.0 ± 0%	11.0 ± 0%	~	(all equal)
NewInterpreter/new_sub-interpreter-2	31.0 ± 0%	31.0 ± 0%	~	(all equal)

[turbolent]

@dete Any thoughts?

[turbolent]

@dsainati1 Should we maybe consider this change for Stable Cadence?

[dsainati1]

@dsainati1 Should we maybe consider this change for Stable Cadence?

Seems to me like based on the discussion on #1252, the sentiment is against these two methods, the argument being that any operation that destroys a resource should be explicit; having methods that can implicitly destroy resources is not a desirable feature for the language.

However I would be willing to put this to a FLIP if it's something we want to push for anyways.

[turbolent]

@dsainati1 Sounds good! Added it to the agenda of the next LDM, maybe we can decide there together if we want to close this and the other related PR, or open a FLIP for them

[turbolent]

Put on-hold for now, see https://github.com/onflow/cadence/blob/master/meetings/2022-10-11.md#additional-storage-api-functions

[dsainati1]

Seems like this feature is not wanted; closing.