Add RT expiration check

[tnorling]

Adds an RT expiration check when available - this is an optimization which avoids a wasted network call when the cached RT is expired. Only applicable to SPA apps using msal-browser

[codecov-commenter]

Codecov Report

Merging #6703 (79bfc63) into dev (81d34b4) will decrease coverage by 3.68%.
Report is 399 commits behind head on dev.
The diff coverage is 62.59%.

Additional details and impacted files

Flag	Coverage Δ
msal-angular	96.73% <ø> (+0.22%)	⬆️
msal-browser	79.19% <ø> (-7.28%)	⬇️
msal-common	84.67% <ø> (+0.13%)	⬆️
msal-core	?
msal-node	80.68% <ø> (-2.71%)	⬇️
msal-node-extensions	69.16% <62.08%> (-6.48%)	⬇️
msal-react	94.24% <ø> (-0.45%)	⬇️
node-token-validation	?

Files	Coverage Δ
extensions/msal-node-extensions/src/Dpapi.ts	100.00% <100.00%> (ø)
.../msal-node-extensions/src/error/NativeAuthError.ts	100.00% <100.00%> (ø)
extensions/msal-node-extensions/src/index.ts	100.00% <100.00%> (ø)
...nsions/msal-node-extensions/src/packageMetadata.ts	100.00% <100.00%> (+100.00%)	⬆️
...-extensions/src/persistence/DataProtectionScope.ts	100.00% <100.00%> (ø)
...nsions/msal-node-extensions/src/utils/Constants.ts	100.00% <100.00%> (ø)
...sions/msal-node-extensions/src/utils/TypeGuards.ts	100.00% <100.00%> (ø)
lib/msal-angular/src/constants.ts	100.00% <ø> (ø)
lib/msal-angular/src/msal.broadcast.service.ts	100.00% <ø> (ø)
lib/msal-angular/src/msal.guard.ts	90.78% <ø> (+0.64%)	⬆️
... and 66 more

... and 187 files with indirect coverage changes