add typeAt function for inspecting the type of objects in storage

[dsainati1]

Closes #1246

Description

Adds a method to AuthAccounts to inspect the type of an object in storage:

cadence•fun typeAt(_ path: StoragePath): Type?

if the storage path is empty, the function returns nil. Otherwise, it returns the type of the value stored there.

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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

[github-actions]

Cadence Benchstat comparison

This branch with compared with the base branch onflow:master commit 0e7825d
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
InterpretRecursionFib-2	2.62ms ± 1%	2.83ms ± 7%	+8.31%	(p=0.001 n=6+7)
NewInterpreter/new_interpreter-2	1.15µs ± 2%	1.18µs ± 3%	+2.91%	(p=0.014 n=6+7)
CheckContractInterfaceFungibleTokenConformance-2	164µs ± 2%	168µs ± 5%	+2.64%	(p=0.035 n=6+7)
RuntimeStorageWriteCached-2	153µs ±42%	133µs ± 1%	~	(p=0.805 n=7+7)
RuntimeResourceDictionaryValues-2	16.0ms ± 3%	15.9ms ± 4%	~	(p=0.710 n=7+7)
RuntimeFungibleTokenTransfer-2	1.19ms ± 1%	1.40ms ±25%	~	(p=0.456 n=7+7)
ParseArray-2	21.7ms ± 3%	21.5ms ± 2%	~	(p=0.456 n=7+7)
ParseFungibleToken-2	443µs ± 3%	442µs ± 2%	~	(p=1.000 n=7+7)
ParseDeploy/decode_hex-2	1.42ms ± 3%	1.41ms ± 3%	~	(p=0.535 n=7+7)
QualifiedIdentifierCreation/One_level-2	3.11ns ± 1%	3.10ns ± 1%	~	(p=0.945 n=7+6)
QualifiedIdentifierCreation/Three_levels-2	163ns ± 1%	162ns ± 2%	~	(p=0.234 n=6+7)
ContractInterfaceFungibleToken-2	46.9µs ± 4%	47.6µs ± 5%	~	(p=0.535 n=7+7)
NewInterpreter/new_sub-interpreter-2	2.07µs ± 2%	2.12µs ± 3%	~	(p=0.073 n=7+7)
ParseInfix-2	23.2µs ± 2%	22.8µs ± 1%	−1.76%	(p=0.022 n=7+6)
ParseDeploy/byte_array-2	32.8ms ± 3%	32.0ms ± 1%	−2.50%	(p=0.002 n=7+7)
	alloc/op		delta
RuntimeFungibleTokenTransfer-2	231kB ± 0%	232kB ± 0%	+0.37%	(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%	~	(all equal)
QualifiedIdentifierCreation/One_level-2	0.00B	0.00B	~	(all equal)
QualifiedIdentifierCreation/Three_levels-2	64.0B ± 0%	64.0B ± 0%	~	(all equal)
CheckContractInterfaceFungibleTokenConformance-2	65.7kB ± 0%	65.7kB ± 0%	~	(p=0.592 n=7+7)
ContractInterfaceFungibleToken-2	26.5kB ± 0%	26.5kB ± 0%	~	(p=0.385 n=6+7)
InterpretRecursionFib-2	1.21MB ± 0%	1.21MB ± 0%	~	(all equal)
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
RuntimeResourceDictionaryValues-2	108k ± 0%	108k ± 0%	+0.00%	(p=0.008 n=7+6)
RuntimeStorageWriteCached-2	1.42k ± 0%	1.42k ± 0%	~	(all equal)
RuntimeFungibleTokenTransfer-2	4.40k ± 0%	4.40k ± 0%	~	(p=0.604 n=6+7)
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	457 ± 0%	457 ± 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)

[codecov-commenter]

Codecov Report

Merging #1254 (c802694) into master (0e7825d) will increase coverage by 0.01%.
The diff coverage is 92.00%.

❗ Current head c802694 differs from pull request most recent head 1fc91ca. Consider uploading reports for the commit 1fc91ca to get more accurate results

@@            Coverage Diff             @@
##           master    #1254      +/-   ##
==========================================
+ Coverage   77.31%   77.32%   +0.01%     
==========================================
  Files         274      274              
  Lines       35347    35372      +25     
==========================================
+ Hits        27327    27350      +23     
- Misses       6941     6943       +2     
  Partials     1079     1079              

Flag	Coverage Δ
unittests	77.32% <92.00%> (+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	89.11% <87.50%> (-0.02%)	⬇️
runtime/interpreter/account.go	93.16% <100.00%> (+0.17%)	⬆️
runtime/sema/authaccount_type.go	100.00% <100.00%> (ø)

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[turbolent]

Nice! Just one small issue in the documentation, but should be good to merge after