test: add tests for page utils

[whylee259]

Description

Adds more tests for page utils

closes: #XXXX

---

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer
• Review Codecov Report in the comment section below once CI passes

[codecov]

Codecov Report

Merging #161 (0ac3e59) into v2/develop (1f739c5) will decrease coverage by 1.87%.
The diff coverage is 68.12%.

@@              Coverage Diff               @@
##           v2/develop     #161      +/-   ##
==============================================
- Coverage       54.99%   53.12%   -1.88%     
==============================================
  Files             812      704     -108     
  Lines           51487    47121    -4366     
==============================================
- Hits            28317    25032    -3285     
+ Misses          20211    19541     -670     
+ Partials         2959     2548     -411     

Impacted Files	Coverage Δ
client/grpc/tmservice/query.pb.gw.go	30.06% <ø> (ø)
client/keys/root.go	100.00% <ø> (ø)
client/keys/utils.go	35.29% <ø> (-3.60%)	⬇️
crypto/armor.go	85.89% <ø> (ø)
crypto/keys/ed25519/ed25519.go	67.34% <ø> (ø)
crypto/keys/multisig/codec.go	100.00% <ø> (ø)
crypto/keys/secp256k1/secp256k1.go	86.79% <ø> (ø)
simapp/test_helpers.go	0.49% <0.00%> (-0.01%)	⬇️
types/address.go	65.71% <ø> (ø)
types/config.go	84.61% <ø> (ø)
... and 74 more