nrf_ble: Expose configuration of max characteristics and descriptors

[andrewleech]

Description

This PR simply exposes a couple of hard defined BLE limits in the config system.
These defines restrict the configuration of larger BLE projects and can't be worked around without changing this file in mbed-os.

This PR does not change the default behavior of these defines, just allows them to be changed by an end-user project.

• BLE_TOTAL_CHARACTERISTICS
  Limits the maximum number of characteristics that can be configured on the BLE stack

• BLE_TOTAL_DESCRIPTORS
  Limits the maximum number of descriptors that can be configured on the BLE stack

Pull request type

[X] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Breaking change

[0xc0170]

@ARMmbed/mbed-os-pan Please review

[cmonr]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 3176
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/7958/

Triggering tests

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/morph mbed2-build

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Exporter Build : SUCCESS

Build number : 2774
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7958/

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Test : FAILURE

Build number : 2981
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7958/2981

[cmonr]

Dang it. Sync failures with NRF51.

Will restart when able.

[0xc0170]

/morph test

[mbed-ci]

Test : SUCCESS

Build number : 3015
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7958/3015

[NirSonnenschein]

/morph build

[NirSonnenschein]

/morph build

[NirSonnenschein]

/morph build

[cmonr]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 3282
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/7958/

Triggering tests

/morph test
/morph export-build
/morph mbed2-build

[mbed-ci]

Exporter Build : SUCCESS

Build number : 2906
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7958/

[mbed-ci]

Test : SUCCESS

Build number : 3089
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7958/3089

[cmonr]

/morph mbed2-build